I just pulled out my stock lifters and compared them to the new Cadillac Racing lifters I have, part# 88958689, and the pushrod cup on the stockers is about 1/16" deeper than the Cadillacs...therefore that could cause a little bit of valve train geometery difference, requiring possibly different pushrod length by about 0.05 or so for optimum geometery.

Just thought I'd post that in case someone else was wondering or used the Cadillac lifters.
I was hoping to use an old stocker to make a solid lifter out of for checking my pushrod length with the new cam, but I guess I'll take one of the new ones apart now

 

same with the comp 850 lifters.. different pushrod cup depth...

 

Did you measure the height from the bottom of the roller to the pushrod cup?

 

What I did was measure first the outside length from the bottom of the roller to the top surface of both lifters. Both are exactly the same at 2.40" with the calipers.
Then I measured the pushrod cup depth just by insterting a pushrod and marking my spare pushrod where the top surface was of the lifter of the stocker.
Then inserting the same pushrod into the cup of the Cadillac lifter clearly shows a 1/16"-3/32" difference, which would have the same effect as lengthening your pushrods by that much if you just swapped to the Caddy lifters and did not remeasure for correct pr length, since the Caddy lifters cups are not as deep as the stockers.

If I had just the right size ballbearing to place in the cup I could use my calipers to get an exact measurement difference. Tried with a short screw but was too difficult to keep straight.