Go back about a week ..WIKD281 was dealing with the same question?..I have had the 8 rib set up (off a150 lightning) running 3.125 8 rib Vortech pulley..No spacing is necessary...If you do you will start shreding belts...went thru 3 belts, before we took a closer look at the alignment.
You need to grind on the alternator and the blower bracket. About 1 hr.'s work...
The problem you are going to have is the idler pulley that came stock from Vortech...It is about 1/4 " too short for the 8 rib and will cause shreding of the belt and burn up the bearings.(The bearnings in the stock idler pulley are not HI Rpm bearings. I blew up 3 idler pulleus and brackets( the bracket is ruined by the idler pulley turning white hot and welding itself into the bracket)
YOu need to have an idler pulley made (cost $75 plus delivery)
Auto Specilities in Stafford Texas can help you on any after market specility parts...They make special parts for all the big racers..