I used the IPD spring s couple of times and all good.
After the first reinforcement ring sold by them snapped at install, I made some from 4140 steel that works well.
The best pump outcome I have had in the form of high and constant pressure was made by selecting the best gear set I had and an alloy case with minimal wear. I lightly polished the gear set so as not to noticably reduce dimensions. I noticed many spare pump's had a torn up gear surface as the main wear location.
I sent the gears off with some of the m41 parts for cryo hardening. Reassembled making sure everything was just so. I think I also lapped the working alloy faces so that the clearances were spot on.
At the end, apart from the gauge reading high on the dash of the p1800, there is noticably more oil out of the top of the rocker weep holes, and I use penrite shelsley medium in my b20 engines. It's thicker than average (and about 1000 times, literally, at reducing corrosive wear in old engines....I wote a paper years back).
Also after all that the pump, when operated by hand, was much smoother than the new pump I also had at the time. Things you do back when you had time for toys ....