[Brian]

Thanks Jim...you're the expert, however, may I suggest you try the 'guts' of a '68' distributor in the clients crab; I think you'll end up pretty damn close to what he wants?
I 'think' it's not the total advance degrees that's the problem, rather, there is minimal spring tension on the weights in an 11A assembly; consequently, they get pretty well full advance just off of idle. The 68 assembly definitely has heavier springs; this has the effect of slowing down the curve.
You've got all the testing gear so I'm keen on hearing the outcome; me, I'm a rank amateur at this stuff, just my experience in trying to eliminate/minimise this horrible noise!!