this whole thing seems fishy to me. has me concerned a bit, using a Gen VI cam setup in my Gen IV block............I just went to Isky website and searched their catalog - seems like there are very few cam setup for the Gen VI blocks - not as popular - not as many to choose from. Also saw some footnote about having to convert to adjustable rocker arms? I'll learn more about it but I don't know if that's the route I want to go.
There is nothing wrong with using a thrust button & the "old method" almost all engines I do are this way but,,,,
It is very simple if you wish to use the late cam retainer:
Everything is the same as what you were originally going to do, the lifters, rockers, springs, pushrods etc are all exactly the same
The only thing that would change is the cam core, the way the cam is retained & the timing set
You are making this way too complicated trying to read into it the things you have to do to the later non adjustable rockers etc.
This has nothing to do with the early heads or any aftermarket head, they have the standard studs, guideplates & use adjustable rockers so all this stuff stays the same.
As for cams, you are not limited to what you see in a catalog
I rarely use a shelf roller cam. A custom is only a few dollars more from most any cam company
You can specify the core you want it ground on, the intake & exhaust lobes you want, the LSA, even a firing order swap if you so desire.
As for timing sets, you certainly do not need the adjustable ones they just make life easier for the installer to dial in the cam.
Sometimes I use them sometimes not but there is nothing wrong with them at least I have never had an issue with them
The majority of issues with them are self inflicted by installers that do not care to use some common sense.
Personally I would never consider a plastic timing set, I have seen way too many of them in the oil pan & this is with stock cams & spring loads,,,,,
But to each his own