Back in 1975 I was running a 1970 Barracuda with a 426 Street Hemi in NHRA stock class, I was looking for more power and ended up checking two and a half set of stock rockers, both narrow and wide pads.
I saw.120 lift differences on the exhaust and right at .100 lift differences on the intake's rockers using my block, cam and stock solid lifter and one cylinder head with soft checking springs with zero lash
I found out later that all those stock OEM rocker SUCK as far as being near the same lift