I only have a pre 86 vanagon, but to replace the strap, it is best to
remove the muffler/cat converter/j-pipe as an assembly, in one piece. There
are about 3 support rods that need to be removed also. This is a bigger job
that it looks like.All the rust makes improvision or air tools almost a
necessity.New bolts ,clamps and gaskets at the exhaust pipe are  necessary
too.While you got this rusty assembly out., it is prbably a good time to
replace the oxygen sensor.You may want to buy these parts from a vender ad
have them avaliable for a local shop to do.Either that , or be prepared to
eat rust.