Elmo, Lugnutz is the Man on how to make your conversion. He and his site were my goto when converting my '51, 3600 to T5 sweetness.
My approach was no spacer. Shorten the input shaft to match the original SM420 shaft length. Same with the input shaft housing. Use a Dewalt angle grinder to lengthen the clutch splines in the input shaft. Then I took the input shaft to the bench grinder and removed input shaft material on the transmission side of the shaft until the clutch had sufficient travel to work without binding. I know this sounds like a recipe for input shaft failure, but keep in mind we're dealing with a less than 100 hp stock 216 engine (in my truck anyway).
The above said, if I ever do another I Will use the Jeep input shaft. It's the easy button. No adapter required and everything works easypeasy.
Also, on a do-over I would Not use a transmission crossmember.
Clutch disk. I'm using a '88 Astrovan 4.3 clutch from Rock Auto,
here.. It actually measures 10.75". Stock pressure plate works fine .
New throwout bearing.
Drilled out tanny case mounting holes to .5", used stock bolts in top holes and two new bottom bolts 2" long.
That's pretty much my story. The original thread is
here..
9 years, 15,000 miles and still happy with the conversion. I did swap T5's to get a better transmission with a .72 5th gear.
Good Luck,
