Could it be a overheating coil..?

As we speak, I'm in the middle of installing a "vapor return" sytem.

Either install (solder, braze) a 1/4 stub into the tank, or up in the fuel fill tube.

Run a 1/4" tube along the fuel feed line back to the tank.

Throw away that "see through" filter and buy either a 33040 (5/16) or 33041 (3/8) wix filter which has a vapor return orifice/ port built in. Install the filter either vertically or horizontally with the 1/4 port on the UP side and hook it to the tube back to the tank.

Take a REALLY good look at your fuel line. On my 67, in the area near the torsion bars, the line comes pretty close to the headers. I'm planning to install a metal shield hooked to the stub frame to separate the line from the headers

There IS a possibility that you have an electrical problem, but the only way this would cause the fuel pressure to drop is if the engine idle deteriorated enough, as in almost dying.

More and more we are seeing problems with the bulkhead connector, and drop across the wiring harness. The general path is from the start relay, through the bulkhead, ammeter wiring, connector at the ignition, through the switch, back out that connector, back out the bulkhead.

That's really a lot of area for problems. Check your voltage drop by turning key on, engine OFF. Put one probe on the battery pos. post, the other on the "dark blue" from the key/ bulkhead supplying run voltage to the ignition/ regulator.

You should see LESS than 1/2 volt, way better is just a couple of tenths.

I recently did some rewiring on my 67, and eliminated the bulkhead connector. On mine, there was a ONE VOLT drop with this test. On mine, the bulkhead connector was a "mess."