Open up that 8 pin cluster on top of the engine. Clean up the male pins
with very fine sand paper (crocus cloth), then roll the paper up
tightly and clean up inside the female contacts.

I have a 1988 305 Cobra and have had to do this every year for some
time. The symptoms seem to be the same with me as you're describing.
Also, it could be the 50 amp fuse on top of the engine.