is there anything apart of the TRANS itself that needs to be built specifically for the LS1? or does that all come into play with the converter and flexplate?

Chris

 

350/400/PG etc will bolt directly to an LS1, one bolt will not be used though. You may have to hacksaw off the ears where the stock inspection cover goes for some headers.

As you stated the converter can be made to work with an LS1 so it bolts right in or you can use a crank spacer to extend the pilot and shim the converter for the proper 'pull out' and then you can use any 'normal' th350/400 converter.