47 V8 ignition mystery

[35fordtn]

The breaker plate terminals can give issues. We have to check them thoroughly during every rebuild. That usually only causes a random miss. You declined the recommendation of a full rebuild on your distributor and only had us adjust the dwell and timing so there is a lot of still unknowns

Only missing under heavy load only with no relative relation to rpm’s sure sounds like carburetor power valve or accelerator plunger to me