68 camaro new installed 16 gallon "REPRODUCTION note OEM?) tank with sending unit rubber ring etc with clams for the hose.

when filling up with gas the gas keeps rushing back up through the neck and spilling onto the ground? Im thinking maybe the neck hose to tank may be on to tight with the hose clamps?

next issue is the fule tank guage works at the instrument clusterwheni turn the car off it goes down 1/4 of as tank when i give it power again it goes back to the normal position? I cant recall if it did this before or if thats normal?

Other tahn those 2 issues everything is secure and works with tha tank installation any advice is greatfully appreciatedthank you.

Ive noticed i cant let the gas pump go full throttle when i fill my 67 or it does the same thing!

The pump nozzles on todays pumps aren't angled as steeply as they were back when our cars were built. With that said when inserting the zozzle make sure that it's verticle and not slanted to the side. If it's slanted some what, then the restriction is enough to cause the splash out, but soon as the nozzle handle is directly under the piping of the nozzle where the gas passes, the fuel goes straight into the tank.

Slow fill is normal. May not be normal with the gauge movement as the one coil, empty side, in the gauge may have alittle more magnetism than the other coil, full coil.