Nothing wrong with your vacuum port, everything is limps' post is good, let be add that I believe this issue prolly is a miss-match at the carb base, limps' carb is a different style but same principle, I would start at the carb, 600 cfm is a good size and will work just fine with some 'tuning'. Get gaskets that match your carb, next make sure that spacer is compatible with the carb base, now it's time to flip it over, check the blades are set to the idle slots correctly, the blade should barely expose the slot, with the carb off set the floats, take a straw and blow air through any holes you can, you'd be surprised what todays fuel leaves behind when dried up
With matching gaskets and spacer you can bolt the carb back on.
Now we work on this timing issue, that may or may not be THE issue, pull the left (passenger side) valve cover, spin the engine over to TDC of compression on the #1 cyl, balancer on zero, both valves on that cyl closed, rotor at #1 spark plug tower.
Get this far and you're ready to crank the engine.
You need toast for 'tun-a-fish' you need a vacuum gauge to 'tun-a-carb.
Get it to idle, set the timing, now the 'fun' begins.
This eliminates 2 unknowns.