Good question on budget. Wheels and tires for under $800 I'd consider a good budget, but people seem to get rid of them for under $500 quite often. I looked at mobsteel wheels and they are $2000 for the full set with tires, trim rings, etc. New Boss 338s are $1000 just for the wheels. I'm sure you can go much higher. For us budget builders, nice wheels are a big deal but may not be in the cards right away.
Some of the Corvette wheels seem to have the 4.5 backspacing you're talking about. I'm guessing anything will need some spacers for the wide fenders of a 3100. Like all things with this truck, it seems like everything cheap is cheap until it doesn't fit haha.
Gotta love the Internet. Here's a build thread where
CaliforniaDaddy used the Camaro SS rims. Looks like 3" spacers on the front :-0
http://67-72chevytrucks.com/vboard/s...d.php?t=639946
