I've done the search and still am not sure. I was unaware there were different ones in the Olds engines until I was talking with my machinist guru today about figuring pushrod length and he asked which lifter angle was in my engine. He said that the camshafts are different for the two different angles and years ago somebody brought him an engine to diagnose with the wrong camshaft for that angle and it ran like crap until they figured out what was wrong with it and put the right camshaft in it. Are there different heads that position the valve train further toward the center to offset the different lifter angles between the two? I see Edelbrock lists two different part number Olds heads that seem to have the same specs.

VERY

My casting number is 396021F

 

You have a 455. All of those are 39° so an off the shelf cam would be fine. The only blocks that you need to worry about are the ones made before the 1968 model year. The 330, the Early 400 and the 425. All 260's, 307's, 350's, 403's and 455's are 39° blocks.

The different part number on the Edelbrock heads have to do with factory class racing, not bank angles. You can swap heads on lifter bank angles with no issue as they used the same heads on both from the factory.

 

The lifter bank angle is simply the angle between the lifter centerline and vertical. The heads do not change, only the pushrod length and angle. The only difference in the heads is that the pushrod holes may need to be opened slightly for clearance if you put heads from a 45 deg motor on a 39 deg motor, or vice versa. Since Olds used the same head castings on both 39 and 45 deg motors, there's plenty of meat in the castings to open the holes. This is done all the time.