fuel filler problems

The stock fuel cap fits as it normally would. This positively eliminates any fuel spillage from coming out the end of the filler tube


So you all do two things...
  1. You install a reducer into the fuel inlet to make it sized for modern pumps
  2. Then you supply an expanding plug that after filling the tank the user inserts into the reducer and expands positively sealing the fuel tank.
Am I correct?