As above, did you check the clearances of the shells before rebuilding?! It's pretty important.......

Also what was the spec of the oil?! Not heard of anyone using Lucas oil in a cossie, plus for ref although Mobil 1 stopped making 15 50 they replaced it with a 10 60!!!!

If pressure was ok sounds unlikely to be pump, how much oil was in there btw and how fast we're you going?! When mine went on my old saph I hadn't checked the oil and was driving 'enthusiastically' and didn't realised I had a leak and spun a shell, actually welded them together