Transmission/rear end conversion 57 Buick

[black57buick]

For almost two years I have tried to get someone to rebuild my dynaflow, something always comes up, don't have time, don't do them anymore or the cost of an overhaul is so expensive, (and the shop is so far away), I would have to sell my house to get it done.
I have been thinking about putting in a GM 400 transmission, getting a drive shaft built is no problem, but getting the correct rear end is something I know little about.
I know there are several options when it comes to converting to a different transmission. What I'm looking for is someone who can tell me where to get the conversion kits and what transmission and rear end would work the best. When I get my car back on the road would like to do a lot of cruising during the summer months.
Vehicle info: 1957 Buick Special, two door hard top. Model 57-46R.

[1957 buford]

I just completed this very swap on my 57 special if you need any info e-mail me at skippetsch@numail.org I'll be glad to tell you everything I did It's not a hard swap