Hi everyone, it's been a while and a lot has changed with my ute. I'm now much happier with it.
I added soundproofing and carpet which cut out a lot of the noise.
I confirmed that my diff is 4.11 by counting the teeth.
So far not going any faster but a lot quieter.
Realised the Heat Control Valve in between the Exhaust and Intake manifolds was stuck open. These things might work in cold places but in Australia I was effectively boiling my petrol (gas).
I couldn't get it to work properly so I'm using a clamp to hold it shut.
Instantly got another 10 mph and it doesn't sound like its working so hard.
Realised my Vacuum Advance wasn't working at all.
Fixed that and adjusted the timing, and it will cruise at 50 mph quite comfortably without sounding like its about to explode.
And it runs a bit cooler too.
Thanks for all your advice.
Bob