Max Conrad (ferried Pipers all over the world in the 40s and 50s) ran
fully leaned & with full carb heat when he was in his max range mode.
Do you know of any reason not to, assuming a low power setting? It
would improve the mixture distribution, something the O-470s are
notoriously poor at. It would also reduce the inlet air density,
allowing things to operate with less pumping loss.

nrp