Vapor lock? In Canada? Not my first guess. Agree with Carl on that. My suggestion is the basics of troubleshooting 101: Wheelbarrow it! Just kidding. Actually it's isolation and testing. Example of isolation is: remove the glass bowl filter, replace with an inline or no filter and drive. Test example, as said: Pump flow test. Make sure you don't have some goofy pinched hose, kinked line. The Rochester is a good carb. Pretty standard design.
I think I read that even though carb was rebuilt "recently", that was months ago? It's been running for
months after rebuild????
I agree with your replacing the pump, it's wheelbarrow but I do it also when it's easy, cheap, suspect and unknown age. Nothing wasted except possibly time. Let us know. Some things have to get worse/more frequent before you can find them. Why don't you just get the pump without the bowl and get rid of the filter with bowl. It's not a filter anyway, it's a sediment bowl. Too many leak paths the old way. Install a metal can filter. Nothing about the old way is good except looks. Glass pumps are 3X more money. We don't need to see the gas. You can see the gas and it's not telling you anything definitive. Just my 2 sense.
http://www.oreillyauto.com/site/c/detail/WIX0/33032.oap?pt=02515&ppt=C0024
