which one

If they are NOS and unused then as PRH mentioned in post 12 the notches in the intake face means 48 degree lifter angle.

The other difference with the 48 degree heads you need to know is that the valve angle is 15 degrees and not the standard small block 18 degrees. If your engine is already built or you have the pistons, while the 48 degree heads will bolt on and can work, the pistons you have now may not be ideal and you need to check valve clearances carefully.

another note is that if the casting date is after, I believe, January 2002, it can only be used with the T&D rocker system and pushrod oiling. The pedestals are milled further and attaching bolt is relocated away from the pedestals center. Also no deck oiling provision is drilled.