I used them. Yes, they position the engine forward a bit, but there are spacer shims. Even with the shims adjusted all the way forward (shifting the engine back), the engine was still further forward than the original position. This actually helped with two of the header bolts that were originally jammed against the shock tower brace, but made fabricating a puller fan shroud a nightmare. I have about 1/16" clearance between the electric fans and the belt, but I did design a piggyback 8-rib drive setup for the accessories and blower (I took a CVF Beast 8-rib and then designed my own piggyback pulley setup for the crankshaft so it's two different diameter drives, one for the acc and larger one for the blower). Unless you are planning something similar, everything should fit fine. I managed to get a double Spal 4000cfm setup crammed in there without interference.