I'm currently looking at a 1983 trans am which had an engine and transmission swap.
The engine is a 1979 350ci GMC Jimmy crate engine (15000 miles). with a 5 speed T5 world class transmission. Im wondering how good of an engine this is (stuff like horsepower/torque) cause im really interested in this car as I will save me a lot of money to get one with a 5speed installed. I'm just questioning the engine cause I don't know anything about crate engines at all. If anyone has experience with these engines please help me out.

 

It is most likely the Goodwrench 350 replacement engine. About 260 gross flywheel HP, and about 300-ish lb-ft. Its primary market was service fleets (appliance vans, construction trucks, etc.). Nothing special about it, some of the older ones were cast in Mexico and had a few issues, If it's got 15k miles on it without problems, it's probably okay.

Various car magazines have taken one of those engines and done build-up articles, typically intake manifold, cam, headers, then usually moving on to heads. Do all that, and they'll make pretty good power. The factory even offers one with an upgrade cam that is rated at 290 HP.

It'll have a little more power than a stock LG4 305, but not much more than an HO L69.

83's didn't have WC T5's, so it would have had to have been swapped in by a previous owner. Have you verified that?

 

Since you posted this in two different forums, I'm going to close this one.