I went with the Weld Racing Pro Star Wheels. They're cheap and classic. I'm also using Mickey Tompson Sportsman radials.

Front
15x5 with 3.5 backspace and GM 4.75 bolt pattern
26x6x15, section width 6.5, tread width 5.7

Rear
15x14 with 3.5 backspace and GM 4.75 bolt pattern
29x18x15, section width 17.6, treadwidth 15.8

This leaves about 23" between the rear tires allowing 1 to 1.5" for clearance on the wheel well sides.