La360 and 727

the low-buck move would be to build the 904 out, and get a proper converter that's already weighted.

the other option would be to sell or trade the 904 (+ cash) for a 727 and then sort out the converter and flex plate. but then you're still in the boat of [likely] needing to build a trans and buy a converter.

so it's kind of a 6 of one situmanation with the added expense if you want a 727

and yes, a 904 will live just fine behind a 360 as long as it's not some super rowdy build.