What do I need to swap from 3spd to THM400?

[Real_McCoy]

I need to replace my 3spd as it has some problems. I have come across a THM400 that I can get for free. I believe it has a long tail housing on it. What do I need in order to make this swap?

I know I will need to remove the stock front crossmember and add one at the tranny rear. Will a crossmember from a donor work? A later model truck?

What else do I need? Flexplate? Torque converter? Cooling lines? Starter? Driveshaft?

I have an I6. I believe it is a 230, but possibly a 250. My father-in-law does not remember the engine that was swapped in 2 years ago. How can I make a positive ID on the engine?

I need to do this soon, but cash is rather low at the moment. Ideas? Recommendations? Advice? Any info would be a great help.

Thanks!

[Chevy Fleetside]

The engine probably makes just enough HP to turn a TH400.. That is a very wrong tranny for that engine.. TH350 would be better or even a TH200 overdrive..