Welcome to the board Geo!
Try this place for springs...
http://www.coilsprings.com/ They custom make springs to original or custom specs. and came recommended by some members of the Riv. Owners Association. I had them make my springs for my 65 Riv. and the car sits nice.
On shocks, I used Monroe gas shocks. Sorry, I don't have specific numbers right now. But, these can be had at any auto parts store that carry Monroe.
For other parts, I have had good luck with these vendors:
Rock Auto (Inexpensive name brand parts, fast shipping)
Rare Parts (Great suspension parts)
Classic Buick (Great for everything)
CARS (Also, great for resto. parts)
By the way, check out the ROA if you haven't already done so. Great people always willing to help out. Well worth my $30 per year. Just a great resource.
Good luck,