18% overdrive crank pulley

[97stanger]

I'm currently running an IW 10% overdrive crank pulley, 8 rib setup, Thump tensioner and 2.85 blower pulley and see roughly 19-20psi. I can get a good deal on an 18% overdrive crank pulley. I am still running my '97 timing cover. I have done some research on the 18% overdrive and am seeing different answers/results. Does anybody run this piece first hand and what type of modifications had to be made? Is it a must to run an electric water pump? I'm also considering going with the 2.7 blower pulley if I swap to the 18% overdrive and I can imagine I would pick up another 5psi minimum with some decent power gains. Just looking for some input on those of you who know/have installed the IW 18% overdrive crank pulley. Thanks guys