I'd have to agree with other respondant who says "take it to a pro".

Having lived through a number of broken or stripped exhaust studs (which I
have repressed the exact number, near four or five), I have learned to pull
the motor, pull the head, and take it to the man. 

If you pay $100 to have the studs drilled out and reset you will rest easy
knowing that it won't happen again soon.

BTW...all of the little hangers that support the exhaust system's weight are
ABSOLUTELY necesary. without them, the weight of the exhaust is pullin on
your exhaust studs. BAD.

GMB, Fairfax, VA
lookin' a '87-'90 Westy
1985 Jetta Turbo Diesel
1976 Transporter (AGAIN?!!)
ex 1976 Transporter
ex 1972 914 2.0
ex 1973 Squareback
ex 1985 GTi
ex 1970 914 1.7
(family) ex 1972 Transporter
(family) ex 1962 Microbus
(family) ex 1958 Karmann Ghia