T-400 was made with Jeep, Cadillac, Buick "round bellhousing. The Jeeps used them in 4x4 applications. I have rebuilt and swapped about 30 of these in different vehicles. If you want an overdrive, then go with the TRUCK 2x4 88-92 700R4. Those years have the hardened sun shells and better lubricating rear planetaries. If you use a minivan 700R4, then the guts are set for a light duty application and you'll have to get it beefed up. If you go 93 and newer, now your into the 4L60E which is all electronic and you don't want to go there unless you have super great knowledge on stand alone wiring systems for the overdrive unit. To me, the 700R4 88-92 would work great, use the aftermarket bellhousing kit. the driveline yoke from the T350 or 2 speed you have now would work great. Once you go to a T400, you need to change the yoke to a passenger style not motorhome style yoke.
I am currently going through a conversion of dynaflow to st400. All I needed was a crank spacer, flywheel, and starter adapter. Russ at Centerville will lnow exactly what you need for any of this. Also has options for OD automatics like 200r4 and 4L60e
Hey DragDoc: You do need the spacer and the flexplate.... You also either need the correct 64-66 starter nose and that will bolt onto your factory dynaslow trans starter or you can get a mini starter. I did that for my 62 Wildcat. I have 3 of the 64-66 starters if you want to go that way to rob the nose and exchange it. The other things you will need if the yoke from a T400 and not a motorhome one. (two different sizes of yokes.) then you will need the t-400 trans mount and take your cross member and you will have to narrow it because the T400 is longer and the mount is farther back. The driveline will also have to be shortened as again the t400 is longer.
Mr 62 that is what I did! Spacers, flywheel, etc. narrowed the trans x member and deepened one side for exhaust to pass. My st400 now has a long 10” tail and later style output shaft. See my other posts to see why
