I need a seal that keeps my truck to stop smoking, but can't afford a rebuild, or new motor, so I was hoping maybe there is something on the maket that I can add to my oil to help on this problem.

There is always a better alternative than the dealership as far as costs. They want to put a new motor in a 2003 model? That is ridiculous to me- cost-prohibitive. Find a reputable independent shop. Look for references and customer satisfaction. A used, low mileage replacement engine is a better alternative, probably less than half the cost of a new engine.
There may be an even better alternative, where you refurbish the top end of the engine-the cylinder head and valve train. This is dependent on that a wet-dry compression test supports rebuilding the top end. What I mean by this is a compression test of the cylinders reveals low compression in one or more cylinders, okay. Next, they would squirt some oil (about a tablespoon) in the low cylinders and check compression again. If compression doesn't change, it points to the valves and valve train (the valve guides which wear and could let oil into the cylinder). But if compression is higher in the wet test, then the piston rings are worn and losing compression, and oil gets past them-this would indicate the engine needs a complete rebuild or a replacement is called for. The reason for the wet test is that the oil will temporarily seal around the piston rings and improve compression if the rings are the problem.
If the test shows the valves are the problem (and it is very possible on an engine with only 120K-your bottom end could be fine), then a top end rebuild of the engine is a much cheaper route than any other choices. You may not know this, but often a little oil burning in the cylinders at start-up is nothing more than the valve stem rubber seals are deteriorated-a real cheap fix. The dealership probably won't tell you this. However, with the loss of power, well, that points to something more severe than valve stem seals. So I would recommend the wet compression test, just to check if it is the top end or the bottom end. If it's the top end, you could have the cylinder head reconditioned and motor along for a few more years, trouble free.
Similar to a compression test, a "leak down" test of the cylinders is actually a more accurate method of finding where compression is lost, and it's only a one step test. They hold compressed air in the cylinder and analyze where it escapes to pinpoint compression loss. Loss of compression translates into loss of power. Have either test done before you decide. Find a good mechanic and trust his advice. (Stay far away from dealers. Greed is their motivating factor.)

blue smoke indicates oil is burning in the cylinders. This is either leaky valve seals, (little blue smoke when engine first starts, but stops smoking shortly after) or the worse problem, worn rings. What happens is when your rings are worn, they let oil get past the rings and into the combustion chamber, AND it also lets out your combustion pressure (your power source) into the crankcase, so you have considerable power loss. Only way to fix worn rings is to rebuild the engine, as just replacing the rings would require complete teardown of engine anyways, and who wants new rings in a worn out motor.

Something internal in the carburetor is wrong, maybe the accelerator pump seal or gasket is bad. Think you will have to put a rebuild kit in the carb. There's no outside adjustment for it being way too rich.

Blue smoke means Oil is burning. You could have a bad seal on one ore more of the valves, bad rings or burnt valve. Usually if it smike right after you start it and then dies down that pints to a bad valve seal, then tend to warm up asnd start sealing better and oil also gets into the cylinders when they set overnight and thus the blue smoke when you start it. very common on older engines and your being an 83 it could be any one of the above casues. Try some of the motor treatments for oil using engines at the parts store. these help the seals be more flexible and help seal better. Other wise you may need a rebuild to get it to stop.

I have owned several including a 2000 that i drive everyday.They have all used more oil than i thought was normal ( about 3 quarts between changes).A new pcv valve will help, i dont belive there is a fix other than rebuilding engine.

TIme for an overhaul and rebuild or a new engine. The rings and seals are shot. This is not going to be cheap. IF you keep driving it, there is an outstanding chance that you will seize the engine

it all depends if its smoking it should only do it for a brief period being that the turbo is reconditioned the new seals have to seat themselves if after about 300 miles it still smokes take it back to the shop that did the repair maybe they left something off or theyll have to put another turbo on your car. hope this helps you.

The blue smoke and oil consumption is because of the bad rings. They are allowing oil to get by into the cylinders and it's being burned with the gas. If you don't want to put the money into an engine rebuild, you can try one of the many additives available at auto parts stores that claim to help restore compression and reduce oil burning in worn or high-mileage engines.

Per previous post. A quart in 750 miles would be extremely high.  A Porsche 930 Turbo Carrera driven hard doesn't use this much unless it's motor is toast, and it is practically a race car.  You should expect at most a quart of oil consumption for 3000 miles.  A quart of oil in 750 miles is a quart EVERY OTHER tank of fuel, and would indicate a motor that needed a rebuild long ago (or seals, guides or rings).  BTW, If you can see smoke in the read view, it looks much worse when someone is driing behind you.  STP or changing to the next higher weight of oil are short term solutions that may help you not leave a trail of smoke.
If you need valve seals, maybe that's it,  but if you need guides, the rings are probably near shot too, unless there are extenuating circumstances.
cheers,

Maybe this would be a good time to rebuild that carburator. New seals, springs, gaskets, maybe the high speed jets are clogged. What year and motor do you have? 302 - 351 - 300?
You should be able to pick up a rebuild kit fairly cheap these days.