Before you do anything....why don't you call the engine builder and ask him which pump he installed???? While you're at it ask him about running 5w30, also as mentioned before, if your clearances are tight then the 10w40 might be a little thick. You could try some 10w30 and see what you get for pressure but it won't make too dramatic of a change.
I've got a stock Melling's M-55 in my 331" sbc and cold I peg the 80 psi gauge. You'll find that most guy's on this forum use the stock M-55 pump, the high volume, high pressure just isn't needed on a street car and in fact can be detrimental in some cases as you eluded to in your original thread.
Last edited by 327NUT; 12-15-2008 at 05:13 PM.