An option might be (if you have an accurate OE 5/16 unit) would be to convert it to a 3/8 line. correct reading aftermarket sending units would appear to be pretty rare from the barrage of reported issues regarding them on here. I had a new (spectra in Canada) tank (tho there are reported counterfeits of em) so I just added a bung in the bottom & left the correct reading 5/16 sender in place & it could even be used for a fuel return.