I ran into this problem recently, its not as hard as it sounds, one, get a different size belt, i had to go smaller, two, summit makes the bracket for like 20 dollars, use the autozone or whatever bottom one but you cant use the one for the top or your alternator, dont bolt it to your intake, just go off the water pump, then make your own back bracket, simple piece of metal with two holes drilled in it, run it from the back of your water pump to the other side of your alternator, bracket should be really sturdy and i havent had a problem at all. if you have the long one with the holes in it ( not the huge chrome autozone thing) already then theres no reason it shouldnt work. about 20 dollars and 30 min of work and your done. part numbers are
SUM-G4019- 65-68 small chevy, short water pump $17.99
SUM-G4020- 69-75 long water pump, small chevy $14.99
SUM-G4021 76-86 small chevy long water pump $14.99
these are the high tech style brackets are what they are called but its what i had to buy and it works
1-800-230-3030 summit racing