Hey there, I have a 72 and made the mistake not to use spindles. you want to start with some 2.5 spindles and 2in springs in the front. For the rear 5 or 6 in. springs. My truck is bagged and I could comfortably run 22" all around without any modifications. My truck came with 15" 295/50 wheels and tires and there is plenty room to go. If you plan on using 20'', this should be the winning formula. Also you should check out
www.porterbuiltstreetrods.com I just recently found him through here. He can sell you custom corvette frontends with rack and pinion steering at a very acceptible price. It will make your truck handle. If I would have known a year ago, that is where I should have started.