[Laird Scooby]

If it's that prone to overheating i'd leave the BFO rad and ATF coolers in place and just not use it to tow anything heavier than a wheelbarrow.

It's possible the liners had a crack not visible when inspected last time, below the piston somewhere, hence my suggestion of getting the piston to the bottom of its stroke and using a boroscope to inspect them.

The Toyota/Lexus was slightly tongue-in-cheek but would certainly give more power and torque for towing and it's a conversion becoming increasingly popular.