Chevy 350 Toni engine dies when put in gear what would cause this

So you are saying when in park engine will idle all day - but when you put in drive stalls - Correct?

I assume you are talking about the GM 350-cubic-inch V-8 engine? If so, there are several reasons why it might die when you put it into gear.

First, I would check the fuel pump or have it checked. If the engine dies when you put into Drive, then it is possible that there is a fault in the wiring to the sender unit. The wiring fault could be a short or an open. In either case, the result is the same -- fuel starvation and an instant stop.

It is also possible the sender has gone. The sender is the device that receives the electrical pulse from the ignition system that tells it to start up the pump. If the sender has gone, then the result is the same as if there has been a short or open in the wiring, an instant stop.

Next, it is possible that the fuel pump itself has gone. If so, your Chevy will have total fuel starvation, once the fuel in the gasline has been emptied, and your car will stop.

Another possibility is your the engine's timing belt. If it has failed then the the spark to the ignition coils will fail and your engine will also fail.

Or, it is possible that -- this is a long-shot -- that your vehicle needs a tuneup. If so, it is possible that one or more of the sparkplugs is failing and the vehicle will stop. If this is the case, though, you will smell gasoline as it will be dumping into the ignition system and will remain unburned.

There's one other possibility and that is the fuel filter. If it is totally clogged then the fuel flow will die and your engine will have fuel starvation. This is a cumulative failure, though, and it is likely that you will notice your engine's performance getting worse and worse until it finally fails.

Checking the fuel pump is somewhat complicated in that you have to locate the gasline and then disconnect it with the engine off. Before you do, though, you will have to put a shallow pan under the engine to catch any gas that drips when you take the gasline off its connection point. Once it is disconnected, if you feel comfortable doing it, have someone key the engine. If the fuel pump is working you should have a pulsing stream of fuel spurting out. Be sure that you only look at it for a second or two, if fuel is coming out, as any more will be a hazard.

I would recommend leaving anything that has to do with the fuel system to a trained local technician as they have the tools and experience to handle this check.