With 20 degrees initial that allows for 15 degrees mechanical. What I suggest is setting the total timing and not worrying about the initial timing. Disconnect the vacuum advance canister and make sure all vacuum sources are plugged off. Hook the timing light up rev the car until the mark on the crank is fully advanced note the degree (I believe on a 273 you'll need a newer style timing light because the mark on the crank disappears because of the location of the timing marks on 273's) now adjust the engine timing to 28 to 35 degrees lock the distributor down and the total timing is set. With the vacuum advance see if it is an adjustable type with the 8/32 Allen wrench inserted into the vacuum line of the canister turn it all the way in until it bottoms out, then crack it back open just a little bit that will be full vacuum assist. Hook the line back up to full port vacuum, not ported vacuum. This is why it is probably dieing at a stop, you have the vacuum advance hooked up to ported vacuum and it only applies vacuum advance when you accelerate, hook it to full ported vacuum and you should be fine.:oops: