Hey guys I am a newbie.
I've got a 1983 Jeep CJ5 with a 304 and I was wanting to put an automatic under it and had heard that a Chevy 350 would work. Are there other conversion out there and which one is better? Any sugestions?  

You heard wrong. No THM 350 will bolt in without some adapting. AMC has its own bolt pattern on 6's and V8's. You need a 80 or later 727 from a 4x4 full sized jeep if you want max strenght or if you can find a 74 to 79 full sized Jeep with a quadratrac full time 4x4 system they had a THM 400 in them that will bolt up. If you go this route though you will need to change output shaft on THM400 as that application has a unique long output shaft matched to work with Q trac tcase.  

I might have a lead on a 727, is there any that I might have to modify?  

tkeltgen:
I might have a lead on a 727, is there any that I might have to modify?

It needs to be a AMC pattern 727 not a Dodge pattern.