I have a billet MSD on my 440. I run Dual Quads. I have my initial set at 16º and I have the black bushing (18º) on the distributor. Have you thought about putting in the Timing Advance Module and playing with your spark advance while cruising..I usually crank up to over 50º while cold cranking...and when she warms up I back her down to >5º. I do go along with the lean burn temperatures others are saying.

A/F wideband is going to tell you whats happening though...an invaluable device