On my 76 coupe deville its all original with 8800 original miles. It has the 500 engine. When i was driving it a few weeks ago, i pushed the gas pedal down about 3/4 of the way downand it started to putter and then i couldent give it more than a half inch of gas otherwise it would stall. i pulled into a store and waited about a half hour when i went back to drive it it ran fine, for about 10 min. then puttering and stalling. I also noticed the gas gague went all the way to full then to e then back to normal anyone got any ideas. I think it might be a gas filter .

Sounds like a possible problem with the secondaries. When you let it cool down, it probably locked them back out (running fine) until they started working again. Has anyone ever "fixed/rebuilt" this carburetor to your knowledge? Thats usually a good place to start. I've seen stuff as crazy as someone left the eccentric off that the secondary rod hanger rides on. This made the secondaries air only, no fuel! And he wondered why it ran like crap and was slow!