When I put the truck in drive, it will stumble and die. This does not happen all of the time, it is sporadic.

fuel filter,coils module.

you have probably knocked somewires loose like cam sensor or crank sensor re check all your wiring near where you did all the work..

I agree it sounds like the magnet for the cam sensor, or a problem in the wiring harness.
I don't think the engine will run with the cam sensor disconnected since it needs that signal to set base timing. It can run without the crank sensor once the engine starts.
There is a slight chance the timing chain is getting loose and affecting cam timing too. You may be loosing plastic teeth on the cam gear.

i had a similar problem with 2007 focus,car stumbled couple times,stopped at store for milk, car wouldn't start back up,alternator light blinking erratically.wound up replacing alternator,actually had the old one repaired,shorted diode.bad job was removing it from car.came out from underneath.

Some makers used Vacuum releases for their emergency brakes which had a Vacuum switch connected to the shift assembly. This would account for a stumble if Vacuum vented out through this switch.

More common for shifting stumble to occur from Park to Drive, engaging a load on the engine, not to stumble to a freewheeling Park position. Sounds like idle speed control is sluggish to stabilize the motor.

You also have idle speed control problem with A/C, kind of shows that A/C was what kept the engine running because when you turned the A/C off, the car died.

I am going to give you some Websites for wiring diagrams. Alldatadiy.com amd Autozone.com with free wiring info upon registering your vehicle.

It seems that the base Idle speed control is not working and the A/C idle speed control is.

Also check for Vacuum leaks on the intake manifold by spraying water from a pumpbottle on the seams of the gaskets.

Check ignition Relay or ignition switch for random cutouts. The fusebox layout is on the Autozone site.

I hope my solution helps.

Sounds like it could be the mass air flow sensor.
Have vehicle scanned for codes and use shop manual to conduct the correct tests on that sensor .

Could be a problem with the ignitor inside the distributor. common problem. beware of aftermarket distributors, like from AZ they are JUNK

either its vapor locking or its the fuel pressure regulator

the distibutor on these models are notorious for going out and then working again more than likely your problem

I cannot see how adding a fuel additive would help to be honest. I would be looking for a split or leaking vacuum line, I have even seen a leaking evap canister before that caused a similar problem. Does the engine pull clean and strong when it is warm or at cruising speeds? Does it feel like its running lean or misfiring?