thanks for the response, i hope thats not the case for me...i was just hoping someone put one of these things on a stock accessory system and that there was a bolt on pulley to make it work.
I think Mancini do a couple of different aluminum crank pulleys. I think they give the dimension from the mounting face to the centre of the groove in the description. I got an ultra shallow single groove one as my alternator is mounted from my motorplate and I have an electric water pump.
Perhaps you could measure the stock pulley depth then look for aftermarket pieces 5/8" shallower. There are some on ebay that give the depth too.