G'day Ripper,

The TB42 bore and stroke are the same - which usually means a motor that likes to rev. Contrast motors where the stroke is longer than the bore - more torque.

I guess the fuel consumption would go from high to very high :-)

I noticed you said heavy towing - I would think about whether this is a good idea in 5th gear, where the gears and shafts are smaller.

I would be inclined to keep it within the yellow marked rev range on the tacho, most of the time