1990 90 Quattro 20V a few questions - fuel line - rear bushing

[TWFAUST at aol.com]

I was recently followed home by another Audi, a 1990 Model 90 20V Quattro.  A 
few problems for which info is requested. The Fuel Pump. Those bonded 
mounting  studs that Audi favors broke and let the fuel pump float. That resulted in 
a  cracked fuel line. Is replacing the fuel line a back breaker? Does anyone 
know  the diameter in case a compression fitting will do? Can those studs be  
purchased? I can't find a VW or Audi dealer willing to help. Rebonding them  
doesn't seem like such an awful job, just time consuming if they were  cheap.
 
Rear Differential. There is a clunk/thunk which appears to result from a  
worn center bushing. Two questions are those bushings available aftermarket. I  
have heard prices in web archives ranging from $20.00 to $190.00. Since it was  
bought on a whim and I have only had slight time to look it over in bad 
light,  are the four socket  head bolts that hold the center bushing to the  
differential double six/tri square, or are they "star".
 
Tom Faust