Is this a fair radiator?

Dana67Dart said
If crank is 6.75 you would need a smaller dia WP pulley to spin it faster.

Or a larger dia crank pulley.

I would leave the crank pulley alone as it should be sized for the other accessories and just make the WP pulley smaller in dia to achieve a faster fan and pump speed.
5.5 to 6 would do it.

IIRC my 273 2bbl is 6.75 Crank And 6 WP stock but don't quote me.

I went back and corrected my wording so it’s now right.

You are right at 10% overdriven with what you have and that’s pretty good.

I don’t have a service manual for years where a 273 was available, but the principle is the same no matter what year you have.