All of your 23 degree headed sbc engines typically uses a standard lifter. Most all of the 18, 15, & 13 degree etc. headed sbc engine uses an off set lifter. Which means that the push rod pocket is not in the center of the lifter and usually on the intake lifter. This helps in keep the push rod as straight as possilbe to the rocker arm. And when you get into the 18 & less degree heads they require an off set rocker also. This is all done also to get the push rod away from the intake ports so they can be made bigger.
TS1955