Hard Starting After Warmed Up.....Arrrg

YES you might be missing something, you need to check the mechanical advance with the vacuum advance line disconnected from both ends (distributor and carb); in this way your total mechanical advance + initial should be 34-36*. With the vacuum advance line connected to ported vacuum on the carb (only pulls vacuum when the throttle is open, not at idle) your total timing should be up around 50* or more at your 2700-3000 RPM point. If it doesn't change then your vacuum advance "can" might be shot. Some say you don't need it but on the street it will really help gas mileage and help your engine last longer by more completely burning the mixture at cruise thus reducing unburned fuel washing down your rings. So IMO it is pretty necessary.

12* of initial should be plenty for your stock-cammed 318 but you can experiment with bumping it up in small increments until it begins kicking back against the starter when you go to start it warm. I have a feeling RRR assumed you have an aftermarket cam but I could be wrong (stock 318 cams are really really tiny).