I have a 51 I6 w/ 3 speed. It would be nice to just swap the engine and roll, but the trans and bellhousing look different. If you are going to use a magnum it might just be easier to use the matching 5 speed. This will get rid of a bunch of that bulky linkage and you can use a hydro clutch. My problem is the I6 runs so nice I almost hate to yank it.