4 5/16" bore, 3.9" stroke.

.030 over = 462".

I've been running late Buicks for a while.
There are a lot of advantages with them along with a few disadvantages.

They are a torque monster - get the 10/1 compression ratio engine and you'll have 510# torque stock.

Drop in on the V8 Buick board as well.
A lot of very knowledgeable guys over there.

Go here: http://www.v8buick.com/