Quote Originally Posted by Dick61 View Post
He used the wrong gearbox. To successfully run a 278 rear with an Aussie you need an M22, if your engine is a V8 then you swap the input shaft in the M22 for the input shaft from a V8 M15. This will give you a first gear ratio of 10.39:1 with the 2.78 diff. This combination will also give a 2100-2200 rpm cruise at 100km in 4th, comparing this with an M20 with a 3.55 diff giving a 10.83 overall ratio you can see that the M22 and 2.78 diff is a good choice as long as you don't want to be a boy racer. The beauty of this combination really comes into its own behind a 308 as the extra torque of the bigger engine masks the wide ratios and gives great take off and cruise. I am going to run a Falcon T5 with the 3.50 first gear behind my 253 with a 3.08 diff, this will give me a 10.78 first with an 1800-1900 rpm cruise at 100km with the standard 0.78 over drive.
just flick the 253 for a 308 and then you can keep it all aussie with m21. the T5 a bit of a drama with tunnel, clutch, cross member and tail shaft?