Converting from a powerglide to a TH350 will require a shifter conversion kit. The drive shaft and cross-member will interchange. TH400 requires ****ing kit, drive shaft, and cross-member changes. The other transmissions will require a bit of work/engineering and more money. Depending on what you're planning to do with the car the latter option is probably worth the effort. Most people I know prefer the powerglide for drag racing. When used with the proper stall converter and a bunch of horsepower they work fine. This is not very well suited for street racing or everyday driving however. Good luck.
