here's the before and after. and what i'm trying to figure out

http://www.67-72chevytrucks.com/vboard/showthread.php?p=1639961#post1639961

It looks like it's a little more than a 4/6. The problem is those front tires look pretty tall so I don't think anything over a 4/6 would work very well.

If you had shorter front tires, I would say a 5/7 is liveable.