BOBSDART has the idea i'm using. Putting the front three major components from a '68 and later 904 to get the better input shaft and larger converter selection into the pushbutton 904. Combine with the B&M 360/904 flex plate. A solid rebuild with a TF-2 shift kit and the little 904 should handle anything a small block can put to a (approx) 3,000 pound car.
I also recommend a rear end upgrade. (because I've got at least six 7-1/4" inadequacy examples piled behind the garage. Kept sticking 'em back in because they were free... but not worth installing even at that price)
I'm also putting discs up front and highly recommend that upgrade.
Anxiously looking forward to your results!