Vacuum Advance Unit Help!

I have a 1983 Golf Mk1 GX  1.5L engine code JB and need to know the vacuum advance unit part number for the car. The distributor is 055905205K and has a vacuum advance unit with only 1 port. All i keep seeing is ones with 2 ports, does this matter and how would i connect it to my weber 36tlp

Looks like Crazy quiffs list a complete reconditioned distributor.

There is usually a code stamped on the rod that connects to the distributor. You'll have to take it off to have a look.