Are the engine coolant temperatures the same? Do you need a new water pump on one engine? Is the oil pressure the same? Do they both idle at the same rpm as before? Engine output the same at top speed?
Are you sure that you didn't overfill one engine? If you did, the oil will get whipped into a foam and rise in temperature.
The next move is to switch the wires on the oil temp senders on the engines or the oil temp gauges under the dash. If the problem moves to the other engine it is one of the gauges/senders.
Bought and read your great book, all other temps, idle speed, output and pressures are the same, oil level correct , I will switch leads to gauges and see if that works.
