Although your posted oil pressure is a bit high, Im going against the grain here and saying its not the oil.....

Ive run 20W 50VR1 in my own driver Challenger and the gear lasted years, I inspected it regularly, but there wasnt any appreciable wear. How many miles?? WAY more than 2000 and 10+ years. And I live in an area where I did start it on some pretty cold days.

You live in Australia, so I assume you arent staring the car in zero degree temps..

I notice you are running a chrome sheetmetal timing cover. How are you controlling cam end play. If you think that cover wont deflect, you are wrong. Ill bet that cam is walking like crazy if you dont have something in front of that cover to limit endplay..

Edit: My apologies, I thought the pic another memnber posted was the OP's. Anyway, how are you(OP) controlling end play? What type of timing cover are you running?

Look into that.

MB