77-85 cars have 5 x 4.75'' same as the Cutlass
There ARE exceptions though.
Some of the wagons have the 5 on 5
and some of the sedans had upgraded 11.5'' brake drums which also had a 5 on 5 I believe.
Also it has been 30 years since then and many 5 on 5 axles have found their way onto these cars.
This fellow is doing the world a service by documenting the cars he works on.
http://www.wheeltool.com/info/5bolt.html#5-4%20%BE%20in
Or you could get a simple gauge for under 10 bucks