That's what I did. I had them cut the spring seat of a 69 slant head till it hit water.
We wanted to find .050 more installed height... 1996, we went with isky pop up retainers and ford 370 springs. Those same retainers, 55.00 then are 155.00 now.
I'd cut .020 and not worry about it. Cutter is same cost or less than pop up locks and retainers to match from comp.
The seat hold springs that exert 300-600 pounds. They are thick.
