You WILL have to space out any FD type damper, and not one of them is the same thickness. Not one.
March Performance makes a pulley kit for the FD offset, but it is 3/4 inch. I have 4 different FD’s in the shop (two FD’s, one PRW and one that I can’t remember which chicom made it) and the two FD’s are the same and the two chicoms are different by about .040 or so.
And, here’s the kicker...not one of those dampers is a 3/4 offset.
If you aren’t willing to pay for the FD brand and get the updated unit with the recessed face so you can run your stock pulleys, or any pulley you want then I suggest you find something else.
