New to Me 1968
the 318 was never built as a performance engine. the heads were the limiter, it did not get the 2.02 valve heads the 340 came with. smaller cam and a little 2bbl.
727 is heavy duty, and heavier than the 904. I like A&A transmissions if you want to have something built.
Home - A&A Transmissions
Even if you are going to DIY, maybe go through their catalog just to see what’s there.
Are you sure it is a 727? 727 and 904 look very much alike. The transmission pan does have a very obvious difference. The 727 is also longer… but that is not as obvious.