You can use GM hei system with your distributor. Just build a small aluminum heatsink for the module to sit on> It's also the ground for the module. Ive used the HEI system in both old dodges and fords and have had many thousands of miles of trouble free driving.
What plugs are you using? Not Bosch platinum I hope they can give you all sorts of wierd drivability problems.
Also dont use premium fuel. If you have any fuel mixture problems when it's cold it'll run terrible.