I think it would be a tuff thing to tune a 284 hydraulic-lifter 340, for a smooth idle,lol; but with solid lifters, what is the net duration after lashing?
IMO, I would be looking into the mechanical end of things before you spend a week tearing your hair out. Especially since it floods the plugs with more than 1 carb, and with multiple timings, and wants very large amounts of initial timing. To me it kindof sounds like the engine is losing cylinder pressure at higher engine temps, or it's pushing gas out the boosters.
What is the idle vacuum at what rpm with what timing.
As you know, those three are intricately linked together by; the T-port sync,the operating PCV, and by even cylinder pressure. Cam timing will raise and lower the absolute vacuum reading, depending on the LSA.
Headers will pull fuel-charge across the pistons at lower rpms, where it will ignite and burn..... in the presence of fresh air, causing a popping out the exhaust. The culprit is usually a header leak right at the heads. The popping diminishes or goes away with increasing rpms,
but often increases during compression braking, especially with a too-far closed throttle.... usually the result of too much idle-timing. With the throttle now closed, the pistons are gonna pull real hard, and they will try to pull spent exhaust gasses back into the chambers during the overlap period. But the headers will be trying to create a negative pressure at that time as well. If the headers are not sealed at the heads, oxygen will find it's way in there, and pop-pop-pop is the result as it ignites. And of course at closed throttle, the intake too is under negative pressure.... so any air getting in there that did not get in there past the throttles, is going straight into the chambers...... with no fuel in it......