Lifter and cam question

pre 68 B/RB's used a smaller ball socket on their lifters. If you see a different part number for lifters and pushrods for a pre 68, I bet this is the difference. I dont think solid lifters had a standard height, they were probably a tad taller to be used with small base circle high lift cams. Check 'em..."These (pushrods) are supplied in factory "B" (361/383/400) engine lengths of 8.575" long. These will work with 1968 and later engines." 440source.com