descent converter on the cheap?

I am not trying to hijack but seeing you have stock heads and a 904 I want to put the high brain power here to the test. Way back 20+ years ago when I was in high school with a 340 Duster I went looking for a bit higher stall when I put my purpleshaft 292 508" cam in. I was told I should put a slant 6 stall converter in but never did because I was running a 727. Will this work for the OP or are there external balance issues to be concerned with? It might be a low cost option?????

I am running a Coan converter and am very happy with it.