Dave
Go with the votes.
What condition is it in first?
Since one of your options posted was to trade it to a purist who wants to do a restoration, are you really motivated to take on the task given the conditio. Yo might want to turmaround and sell/trade it in for something you really want, or use the cash to build up any project you are currently working on.

That being said, the 63 Riv is a sharp car and would make a great
custom. The style is sharp, The interior is one of the best looking of all early to mid 60's icars. The 401 is a rare engine and runs strong.

About a year ago I remember reading a Street Rodder Magazine issue that had a 66 Rivera ( Alittle different but close in looks to teh 63) The car came out great. It had cosuom Grill work done, chrome wheels, deep blue paint etc.... Yo can easily update th esuspension with that car by incorporating suspension parts from later model Buicks and Caddys. Go to Barnes and Noble and get an interchange guide. You will find out that your search for parts will be easier than you think.

If you decide to customize it, I would suggest not going too radical, but slightly improving what is there already ( Adjust the stance, Cool paint job (House of Colors paint and two tone paint jobe really bring out the lines in that car ) , update the interior a little, Dressup the engine compartment , removing any excess chrome/stainless trim that was on some models and chrome wheels (Go with 17's) If you live in the Northeast yo will have to deal with potholes and older roads. NO WHITE WALLS PLEASE!!!

Good luck with whatever you decide.