Okay, another update; I keep getting sidetracked so this is taking longer than I thought.
I installed the new LS7 lifters, trays and got the heads back on so I was able to check the pushrod length to see if my theory was valid; I appear to be wrong.
This DOD engine uses the same pushrod in all 16 lifters and all of mine were in good shape as were the rockers & trunions.
I used the method of determining the lifter preload by placing each lifter on the base circle, using a known length pushrod (in this case the factory 7.385 pushrod), running the rocker bolt down until zero lash, and then counting the additional turns needed to seat the rocker in the trunion.
There is a formula for computing how far the lifter plunger is depressed by the amount of turns needed but to hit the factory specs you want to see between 1 & 1.5 turns; most high RPM performance builders look for 1.25 to 1.75 turns to promote valve train stability at higher RPM'S. This sets the LS7 lifter plunger between the halfway point and 75 percent of the plunger travel.
On my engine the DOD lobes with the standard LS7 lifters took 1.5 turns to seat the rocker, which is within both the factory spec and the performance spec.
The non DOD lobes with the standard LS7 lifters needed 1.3 to 1.4 turns to seat the rocker with the same factory pushrods, this indicates that the DOD lobes have a slightly larger base circle than the non DOD lobes on the camshaft but so slight that valve train operation should not be effected in any way as all are well within the proper specs.
So this means that the commonly reported issue of trying to do a DOD delete without changing the cam does not work well due to the DOD cylinders ending up with dramatically less compression is not caused by incorrect pushrod length on the DOD cam lobes (as I theorized) but is caused by some other profile difference in the cam on the DOD lobes.
At first I decided I would just start tearing out the radiator for a cam swap but I decided to wait till tomorrow and do a compression check first, mainly because I still cannot imagine a lobe profile that would cause the compression issue with the proper lifter preload geometry (as I currently have).
If my compression test tomorrow reveals the dreaded low compression on the former DOD cylinders I will say uncle and change out the cam but I still will not understand the cause; if I don't have a compression issue then I will finish assembly and see how it runs.
Hopefully tomorrow will shed some more light on the subject