Does anyone know a manufacturer and part number? I would like to eliminate the rotators and use normal retainers on the exhaust springs. I don't wanna pull heads again for any machining. The heads have the spring seat for exhaust valve springs cut apx 3/16" deeper to accomodate for the thicker exhaust rotators and keep installed height correct. I would need either a taller spring with same 1.260 OD in the 105-115lb range or a spring seat cup that won't require machining or a .1875 shim or a special retainer.