Mad , how did we get from sucking the pan dry to wanting 40% more. Not sure I believe the .350 taller. 250 pump gerotors are about .875, the 427 FE (I think, they were unboxed with only a tag, bought 20 years apart and were the same) height at about 1.100 for a 26% increase. It worked fine for what I was doing drag race only. 48 years ago, I was new to turbos and did not know how much oil It needed so I did the tall gerotors. New build I am not doing it just shimming the spring for 60 LBS the 250 pump is about 12% more than a 200. A shimmed spring 250 pump should work for what you are doing, keep in mind that the small six dist/oil pump and cam gear is on the small size and adding more load than necessary is not wise.
Sorry I do not have a good way to do pics. A taller cover would work better than a spacer one less place to leak and stronger, these things need to be machined flat and exact.
Maybe we can get some people to measure their pump gerotors, so we know what is what. It is possible that a stock 300 pump is 1.100 tall not sure, never had one, used what was on the clearance table.