Vacuum Advance Issue

[69GMCLonghorn]

Hey guys, haven't been on here in ages. Now working on a 70 Custom/10 longbed. It has a stock 2 bbl on a 307. When I bought it, the vacuum advance diaphragm was blown out, so I just advanced the distributor a bit and capped it off. Worked fine. Well, through the course of several carb rebuilds and now finally upgrading to HEI, I reconnected the vacuum advance. It is connected to the port on the carb that is midway down and pointing at a 45° angle toward the front. It is basically getting full constant vacuum instead of ported vacuum, resulting in an instant 25° of advance as soon as I hook it up at idle!! No wonder the old diaphragm blew out. I've tried the other 2 vacuum ports on the carb. One is the exact same and the other one doesn't have much vacuum at all (I think it went to the flapper valve on the original air cleaner.

I'm not at a point where I want to do a manifold/carb swap to a 4 bbl. I just want this to work for the moment. Any ideas on what's going on with this thing? And more importantly, can it be fixed??