HH56 wrote:
Does the engine just die or does it stumble like it is running out of fuel...

If fuel, if the mechanical fuel pump is still in and fuel still flows thru it, what is the condition of the screen inside the bottom cover and sump.

If that is not a possibility, how is the vent in the gas cap. Another remote possibility some have experienced is debris in the tank moving around and blocking the fuel intake. When engine quits it floats away. With an electric pump, probably not as likely unless the electric pump also stops long enough to break the suction.

If it just quits suddenly, many have had issues with coils overheating and quitting. After current stops and they sit and cool for a few minutes, all is well again. Same could happen if capacitor is acting up when hot.

PackardV8 wrote:
THe drop off of power at 45 mph is a clue. Does i make a kind of a pup-pup-pup-pup sound just before it dies??? Try a KNOWN good coil and condenser first that's the easiest. OR REMOVE gas cap if vent is plugged.

If those fail to cure the problem then very likely it mite be a needle and seat problem especialy if needle is "rubber" tipped and distorted due to ethanol or a bad pump.

joeyearl wrote:
If it were the condenser, it could gradually begin to run poorly from idle throughout the operating RPM range. Eventually it wouldn't start at all.

Old, weak coils can fail after getting hot, and function again after cooling. But it takes an hour or two to cool down a coil.

Sounds like sediment in the tank to me. (IMHO).