Dieseling is caused by 1) incorrect timing (if you don't hear pinging, it's more likely too far retarded than advanced), 2) incorrect mixture (are the throttle shafts on your SUs rattling around in the carb bodies? That's a fine variable vacuum leak).

My opinion (refuted by some) is that the tall head gasket does very little to reduce pinging and a lot to reduce performance and economy. Compression probably has little to do with the problem, so I don't recommend these.