The carburetors should be good, Cliff seems to know what he's doing. If not heat or lean condition then it's timing or high cylinder pressure. I know it's been five years but why not call or drop in to see the engine builder? Just ask him what he thinks about the detonation, can't hurt and he may be able to give you the answers you need. He knows the engine better than anyone, he built it.
Remember every engine is different, especially when something as critical to engine running characteristics as the camshaft is changed, factory and accepted modified specs for timing wont work the same with yours as it does with one like mine. Factory specs go out the window. Mine runs best at 28 degrees total and 16 initial. My distributor with 20 degrees mechanical got some modifying to get it to work in my non-stock 428.
I know it's been mentioned before, I forgot if you answered, did you check the timing mark is actually at TDC?
