1963 Riviera transmission swap

Just picked up a nice rivi with of coarse a bad dynaflow, need someone to refresh me on what transmissions will fit with out adapter, I think a 64 or 65 switch pitch?? but want clarification.

 

I have a 64 Electra and when we swapped in a 63 Wildcat motor, the 63's ring gear was on the converter as opposed to being on the 64's flexplate. Couldn't really just swap parts to bolt it together because Nailheads are externally balanced by the flywheels/flexplates from what I understand. So we yanked a 64 401 out one of his parts cars and its run perfect for the last 20 years. 64 was first year for Turbo 400's too, I just sold one a friend to put behind his 59 Nailhead motor.
I remember an ebay store that we've both used called something like buickrodder. You may look for him on ebay, I'm sure he could help you out.

 

64-66 st400 or sp400 will work, you'll need the flexplate and converter as well..
65-66 is perferred as the valve body for 64 was one year only. The 65-66 stuff is more general TH400 stuff. You'll need a bushing (standard bushing I just needt o find what it crosses to) and to either enlarge the hole in the flexplate or turn the crank end down. I find it easier to enlarge the flexplate hole. The bolt pattern is the same. You'll need the starter as well. Can't remember if the 63 needs one hole drilled and tapped for the starter or not, but I'm pretty sure it does.

 

I've had great luck out of the st400 in my 64', if that's any help. Maybe you could just get one rebuilt, any regular transmission shop should be able to handle it since basically a th400.

 

65-66 ST400's are switch pitch and dual range. 64- no switch pitch and single range. Any will work with your nailhead, with of course the flexplate mod. You should stick with Riviera ST400's so that you won't need to modify the driveshaft and trans mounts.

 

i understood 1965 was the first year for the TH-400, except for the Cadillacs. Those 1964 Caddilac TH-400s are rare and in high demand, because it was the only year the TH-400 ever came with a bellhousing mounted starter. Don't know about the Nailheads, but they are popular with the pre-1965 Pontiacs.