Funny thing is: I also have a '91 roadster with 12gal and 480s.
I just use the stock seat belts as lap belts.
But then I have'nt had to go for inspection just yet, since I cut the top not too long ago.
I would say to do it like RICK and LINN are saying to do it.
My 2 pennies.
isenegger
+1y
thats what i did i just made some mounts right below the top of the cab.
snoplow
+1y
i did the center bench belts as well. just make sure you get the female part as not all males are interchangeable