transmisson queston

[90\87Formula]

It's been a long time since I went to a TH400 from the Powerglide.
I think (not for sure) you'll need a different flexplate. You'll need shifter linkage for a TH400. The driveshaft will depend on whether you get a long or short output shaft TH400. The kickdown switch on the TH400 is electric and can mount on the carb or on the gas pedal.
The PG crossmember can be used, but I think it has to be moved. There are already holes there though, so you don't have to drill any.
Torque converter for a TH400.
Like I said, it's been a long time ago, so there is probably more I didn't think of.
TH350; I don't know anything about. Never had one.

If you're going to get rid of the PG, sell it to a dirt-track racer. Like Gray Ghost said, they're worth some good money to those guys.