i'm putting the engine back in my Jimmy, and didn't know if you had to fill the torque converter itself or if you could just fill the tranny itself once it is put back together. Its a th350 if it matters.

You should not have to 'prefill' the convertor just make sure that it is in all the way

also, don't just dump 8 quarts of fluid in the trans and then start the engine.
correct procedure for a newly rebuilt trans:
install converter in trans
you can put some fluid in the converter, but not essential
put 4 quarts of atf in trans
start engine
immediatly dump another 4 quarts in trans
run trans thru gears
check fluid level and finish filling accordingly

a th350 should hold 8 or 9 quarts, a th400 and th700 just a bit more.
if the trans was not rebuilt, it'll take a lot less fluid if only the pan and converter were removed. probably 3-4 quarts total.