Bob, isn't the 1996 engine computer controlled? If "yes", is that computer/sensor/ignition stuff compatible with a 6 volt ignition system?
It seems that connecting the oil pressure gauge would be the least of the challenges. That would simply require an adaptor available from Speedway Motors.
Presumably the purpose of the engine swap is to occasionally let that V8 power press you back in the seat as you merge onto the freeway or dish out a dose of tire smoke to a rice rocket. I understand those engines make about 400 ft/lbs of torque. How will you keep from exploding that 61 year old transmission and rear end?