There is your problem, Roger, you are overdriving that pump by having a smaller pulley on it. That was my problem too. The correct pulleys were discontinued by Ford Racing but Runne Rite used to make them for Ford and still carries them. Once I ordered the right ones it was VERY apparent I was killing the pumps myself by having the wrong pulleys on them.
In the picture below the pulleys on the left are the wrong Zoops pulleys I had on it. The ones on the right are the correct Runne Rite pulleys, You can see how overdriven it was, and yours is similar. You will never keep any gasket in that pump with that overdriven condition..............I had to learn the hard way, about $ 1500 dollars worth of screw ups later, if you factor in 3 pumps, two sets of pulleys, U Haul truck and trailer to bring my car back from Daytona, etc. But it is finally working great after I got the right pulleys.
Also, I don't know if you can see on Don's car (blue one) but the stock Ford wp pulley is huge compared to the crank pulley, slowing it down even more.
Don
BTW, here is Runne Rites website: (Oh, and all of those pulleys shown are billet aluminum, they just photographed black for some reason.....reflection?)
Pulley Kits