I have a 1994 s-10 that I want to put a th400 transmission in. Im curious if I can mount the th400 directly to the motor(4.3L vortec)? I was told that the 4.3L vortec was an identical block to the 350, just missing two cylinders. If anyone has an answer to this that would be great.

Thanks,

It's not about the engine size. It's about the transmission. And how it works with the vehicle.
There are a number of things that need to be taken into consideration before a single bolt is removed: How will you shift it: floor or column? How will the Engine Control Module (ECM) know when to start the engine (neutral or park)? Will the speedometer work? Will the back-up lights work? Are the mounts the same? Will the transmission physically fit into the truck (length, mounts, driveshaft, etc)?
Have you considered selling the truck and simply buying one that already has the transmission you want?

Im trying not to get rid of it. I've spent over 3,000 in it over the last couple of months. I just can't get the manual transmission to bleed all the way. Ive replaced everythn from new motor to clutch, preasure plate, throwout bearing, slave cylinder, clutch master cylinder. Ive takn it to 2 shops and they can't get it either. One of those freak things that happen I guess. Ive got a th400 sittn in my shop. I was told that everythn would work, speedometer, lights, mounts blolts, and drive shaft. All I would need to get is a B&M mega shifter. Which comes with the park and neautral switch. I just want this project to be over with!