You need a 2nd cooler with a 3.0L.
The 76 3.0 Turbo I had was horribly undercooked with just an engine mounted cooler and the trombone cooler. It was fine while driving at speed but when I took it to Luft in 2019, I had to keep shutting it off in LA traffic to keep it from overheating.
My 77 track car was fine with the trombone when the engine was stock. When I rebuilt it to high comp 2.7 RS spec, the cooling system was no longer able to keep the engine cool at the track.
I installed a RX7 cooler spliced into the trombone cooler and everything was fine.
https://forums.pelicanparts.com/porsche-911-technical-forum/492336-budget-oil-cooling-myth-dispelled.html
All these years later and lots of street and track use, car still running fine and the factory scavenge pump had held up fine.