Very weird and intermittent starting issue

[kaysboat]

I'm having a very aggrivating starting issue with my 1980 straight 6 three on the tree.

For the past couple of weeks the truck would randomly fail to turn over (as if it had a dead batttery). After a couple minutes of sitting, it would then fire up no problem (no labouring etc...) The issue has become progressively worse to the point now where it rarely tirns over. The lights, and radio work fine, but when turning the key to start (with clutch depressed) nothing happens.

I thought the starter solonid may have been the issue, so I changed the starter. Same issue. Bench tested the coil (integrated into the distributor cap) and I think it is fine, although I wasn't entirely sure what the readings on the multi meter were supposed to be.

I had the battery bench tested which turned out to be shot (no amps registered on the tester), so I charged up another battery which is less than two years old, but the problem still persists.

Any ideas or more troubleshooting tips?

Thanks.

[old Rusty C10]

Check all the connections of the battery cables and grounds

[walkerb]

Neutral safety switch? Any difference pushing the clutch pedal harder or softer?

[kaysboat]

Yes. It seems to start pretty reliabily when the clutch pedal is depressed about 3/4 of the way. Does this indicate the neutral safety switch?