From the other sources like with the Spectra tank and with the Spectra sending unit. They were the same thickness. In addition my original 1967 locking ring was about the same thickness as the Spectra replacement. Then a couple of years ago I went to a local Mopar show and a guy was selling new repo rings. This ring was definitely thicker; you could tell by the feel of it through the cellophane wrapper.
For best results, measure your old ring/gasket and your new ring/gasket, and install it with the tank off the car to see that it fits properly.
