3000 for a late 235 is about right for max sustained rpm.
I got a 3.55 rear and take a 250 mile round trip on the freeways, every other month.
I found at 2500-2800rpm the engine runs near thermostat temp consistently.
If you go 3000rpm or higher or pull up mountains, engine temp creeps up a bit, especially during summer in the desert.
One of the last super hot days in September, I brought my new rebuilt 261 home on a 3500ft mountain climb of 100ft/mile.
- Never seen my old 235 that hot around 1500-2000rpm.
Max sustained rpm definetly depends on the weight and terrain.
I know my new 261 with the same driveline, but 1200 lbs. lighter weight will stay cool and allow higher sustained rpm.
