s10cnyncrvr (Jeremy) who never posts anymore had a setup using existing bolts for the upper seat belt hangar, and hung a bar across from there.
unfortunately i can't seem to find pictures of it with a quick search, maybe someone else remembers the setup.
one point to note that i've heard about on the internetz (take it with some salt), nice racing seats with a nice harness may be more harmful in a rollover because crap seats with a stock 3pt belt will allow the roof to cave in and the seat buckle, allowing for "headroom" to open up.
a nice seat and harness will keep your head in the same spot, allowing the roof to cave your head in.