Been there done that. If you can keep the fuel injection, do it ! They are reliable, start easy, and look so great in an old car or truck. There is an outfit in Arkansas called Street and Performance. Get their number from their web site and talk it over with them. They will give you a real live technician to talk to. A new wiring harnesss comes with their computer. Hardest part of the F.I job will be the new fuel return line you will need to run back to the fuel tank (all FI's recirculate fuel) and an electic fuel pump (since the one in the van stays with the van in the van's fuel tank). Since the engine is coming with the original trans., the trans TV cable and the linkage should all be the same, so the trans should work like it did in the van. In fact, you could pull the computer out of the van along with the wiring harness to it and shorten or lengthen the wires to fit your need. I don't know how mechanically tough it will be to mate the trans to the '51 drive line, but that will be an issue regardless of whether you use F.I . or carb. Come along into the 21t century and go for it.
