Replaced fuel gauge transmitter and gauge now reads 1/8 to 3/8 instead of Empty to Full. Removed transmitter and simulated full (upside down) and empty (right side up) and gauge showed these values. Replaced transmitter into tank and it read ~1/8. Added three gallons and it read a little less than 1/4. Filled tank and it read 3/8. The only calibration descriptions I could find on net are for aftermarket VDO.
Is there a way to get my original gauge back into calibration? Or what do I not understand about this situation?

You could try adding a resister (less than 100 ohms) onto the signal wire. Not sure if it would open up your gauge range or simply shift your existing range. Easy to do. Worth a try.

So you've found that with the fuel sender out of the tank and right side up, the gauge reads empty. Is this correct?

Does the low fuel light come on?

It would seem that simply placing the sender in the empty tank would not cause the sender to move and thus the gauge should still read empty.

Does the full/empty test give the same result if the sender is grounded to the tank or chassis?

Is the new sender for a 914? Where did you procure it from?

I bought a new Bosch sender unit from an outfit in AZ for about $150. The installation was easy & the gauge works fine now. Plug & play.