Cherokee fuel sending units

I have finally had enough of the bad sending unit on the right tank.
Since I want the beast in and out quickly, I figured I would get an
exchange unit from Airparts of Lock Haven. $500 core charge? Yikes! I
guess they REALLY want that core back!!! I believe the "stock" sending
units/gauges on a 74 Cherokee were Stewart Warner. I believe they made a
replacement Rochester combo and they are not interchangeable. Is this
correct?

I have had these pups (fuel tanks) out in 1999 to change the sending
unit gaskets, replace the main fuel lines, and replace the overflow
hoses. I replaced the tank screws with the proper structural stainless
screws. Can I reuse them? I do not recall anything saying they were
"one-time".

Thanks,
Mike