ok, is an amc 304 and chevy 350 interchangeable as far as with the stock tranny out of 74 cj5?

While this doesn't answer your question, it is a great source for info on swapping engines out on older jeeps.

http://www.novak-adapt.com/

The Chevy engine will not bolt up to the Jeep transmission. However, it can be converted to fit, and is a good choice, mainly because it (and it's parts etc) are far more plentiful than the AMC engine.

Such a conversion is easier if you have an automatic transmission in the Jeep right now.

If you have a manual transmission, you will need a Chevy engine with a pilot bushing installed at the rear of the crankshaft. Most 350's that were installed originally with automatics do not have provision for such a bushing, although a decent machine shop can install one for you.

That site shown above is great for info on such a conversion.

Is your existing transmission a manual (3 spd or 4?) or automatic?