73 busses did come with dual carbs, but it's such a tricky system to keep
going that a lot of people put in a single carb system. It's an aftermarket
kit. I hear it s better.   Those facing expensive fuel injection repairs
 have been known to do the same. 
the distributor number's on the side of the distributor.  

I started doing my own repairs after I got ripped off, too.  But I'd go to
the vw parts store and bug them for advice. And ask friends, who sometimes
knew what they were doing.  I know I did some dumb things, but I saved a lot
of money, and I like the satisfaction of doing it myself and knowing my
beast.  

  Good luck 
C lara Williams

my first bus was a 73 westy