280Z fuel sender unit in 240Z tank?

[tannji]

I recently obtained a new Sending Unit from Jdarkme for the 240Z fuel tank resto I have been doing. I noticed immediately that it was not exactly the same sender, but chalked it up to being newer and updated. Upon hooking it up today, it registers bone dry as 1/4 tank of fuel. I was wondering if anyone has input to this before I try field-engineering it mechanically or electronically. I looked it up at MSA and there is apparently a model-year change at late 1974, and the newer part is almost double the price... but I obviously don't know what the difference is. I just spent an hour cussing the car, the tank, and my forgetfulness... (Note: it is MUCH easier to reconnect all hoses before installing tank straps!) I don't particularly want to pull the tank again, so any pertinent info would be welcome = )