I don't remember if I pulled them out of a Healey's engine, or an MGB, but there are factory shims that were available. Once I discovered them, I'd put one (1) in every engine I'd build thereafter__somewhere between 112-120 A, B, & C Series BMC engines. You'd get about another 10 psi of oil pressure with them.
The "new" 1500 Midget engine didn't respond quite the same way__as I watched a spin-on oil filter start BULGING as soon as I was raising the RPMs with my hand on the throttle! Unfortunately, I didn't reach the key before a seam split, but the mess was minimal and I didn't have it spraying the engine compartment.
Funny, I only built one (1) ever 100 engine; back in the late 70s, most of the ones we'd see had cracked cylinder heads, making them ripe for sbc-swaps.