That still doesn't sound right because...
my lifter plungers are depressed .045 to.05.
The lifter would've taken up the .020".
And I don't are what anyone says... wearing out a lobe on a cam inside of 25 minutes just doesn't happen unless there's some seriously mis-matched parts, or some really bad initial adjusting going on.
Which brings me to ask:
How are you setting/confirming the valve lash?
(Adjustment is done by using different length pushrods if necessary)
FoMoCo gave you the Stock Length for the pushrods of a STOCK motor.
They don't know if you had your heads milled, your block decked, how much the valve seat was machined durring your rebuild, what springs you're using or what height they're installed at, or if any of the rocker studs are still at the stock height.
If any of these were done then the length that FMC gave you is worthless.