Big Block/A-518

I'm going to use an A-518 behind a 440 in my Duster. I know I have to modify the floorpan and fab a trans crossmember. My question is with bolting the small block trans to the big block. The only adapter kit I've seen so far is from SMR trans and its over 500 bucks which is too expensive as far as I'm concerned. What other companies have adapters? I assume that the swap is the same as bolting a 904 to a big block. Is there anyone who has cut the bellhousing off of the A-518 and installed an SFI approved one and/or will an SFI bellhousing for a 727 work? I'd consider paying 500 for something like that but from what I've seen of simple adapter kits is that all you get is a plate, some bolts and maybe a spacer for the flexplate.