Advice Needed - Can't Start Rebuilt 273

Correct cam-----No need to "hope", just check it. You have the cam card, and as I said, even if the balancer is not degreed, you can calculate degrees per inch around the perimeter of the balancer. You can verify cam opening/ closing events. Even the shop manual gives you this for a stocker to check for a slipped cam drive. You can even ESTIMATE, look at the cam card. Exhaust closes 8* ATDC. You can just look at the timing marks and guestimate that

Correct timing marks.------- No need to pull the balancer/ timing cover. Use a dammed piston stop. Forget this wire in the spark hole B.S.

You said you "did all this," so why won't it run?

If it's puking flame out the carb, either a valve(s) is stuck open, or is open at the wrong time, or the ignition timing is wrong.