Looking to replace my 273 with a 318, which one?

Well, I called the dealer and they don't have any 85-87 318's left, and the VERY helpful parts department guy (who has a 64 cuda), Said I'd have to have a torque converter made to use that 318 with a 904 trans. So what all is involved with going to a 360? Will a 904 trans bolt up to it? What would I have to do as far as motor mounts? Does a 727 trans fit within the stock 65' Barracuda trans tunnel and work with the stock floor shifter? Anything else to look out for? Thanks buds! :prayer: