Soooooo, have spent the last 7 days with the GT finally out on the road and have clocked up just over 600km to become acquainted. During that time I have made many an adjustment stop, both voluntary and involuntary! I ended up swapping back to the weber as the solex was just too worn on the primary throttle shaft. I found the problem with my Weber, manufacturing swarf which was easily removed with a full strip and air blow out. Had a few breakdowns due to ignition drop out (tachometer zeroed as engine cut) which turned out to be an easy fix in regapping the pertronix. Finally gained full confidence yesterday and stretched its legs on the french highway (risking expensive tow recovery and fines) with a max of 175kph but more in the bank. Although the new refurbed hydraulic lifters are tapping and need adjustment again I'll conclude by declaring my undying love for this car..its my first GT and such a good fun thing to own. The locals here are fascinated by it. As for the Isky cam, I'll look at that again next winter. Thank you to all you guys for your help, input and thoughts!If it works for you, and if the result is a lifter that is accurately adjusted such that the lifter plunger is partially depressed, and not bottomed out, and since it is your engine, then no worries.
One issue I have encountered on brand new hydraulic lifters is that they are SO leak-down proof that they do not allow oil to be expelled from the lifter cavity when the adjusting nut is tightened. If so, they act like a solid lifter, and tightening causes the valve to un-seat. The solution is to pull each lifter out just before the rocker is adjusted, and carefully depress the plunger in a vice, expelling the trapped oil. Then install the lifter, and adjust using the correct method. Within a few hours of operation, the lifter will adjust properly.
For clarity, there is no reason (none, nada, zilch) reason to adjust hydraulic lifters with the engine running.