In my HG I had a t700, 2.78 Banjo diff and 265/50r14 tyres.
It was fantastic on fuel and would do about 2100 rpm @ 110km/h
It cruised to Bathurst (and Canberra on a different trip) and was getting 32 mpg.
Worked 308 with a 465 holley. (Also had A/C and P/Steer)