i did a cost comparison between beefing up an A518, and a gearvendors unit, and taking the converter out of the equation [every application will be different, and a good converter isn't cheap], the A518 rebuild, plus the UltraBell needed to attach the transmission to my big block, it was cheaper to go this route and the overall length was a bunch shorter than the 727 plus the gearvendors unit.
i too, was put off that gearvendors wanted the "????" adapter back before they would "sell" you the one needed for your application.