In the first rendition of my Fummins, I chose to make a hybrid motor mount utilizing the 7.3 IDI mounts that were in the truck. I cut out a plate and drilled holes to match the cast mount bolted to the 1st Gen bolck, and basically bridged the gap between the mounting plates and the stamped piece from the 7.3 block.
Probably not the greatest solution, but it worked out pretty slick. The benifit was that I didn't have to change or hack up the crossmember, and I could use the stock Ford PN for the mounts. I also liked the idea of the Ford mount better than the chinchy 1st Gen rubber block.