I am Liking The Redline 30WT 10w30 Racing Oil to try out this Fall in the '76 Pontiac 455 engine.
The Redline 80w140 Gear oil I used in the '63 Pontiac Gp 9.3 Posi Differential dropped oil temps checking touching by hand after several long 100-110 mph runs on the Highways for 10-15 miles nonstop.
Touch the back housing of the Differential and it's just warm to the touch around 105 F.