Gas back splash while filling gas.

[maxtruck]

Somewhat at a loss here, just bought this truck a 73 C-20 and like it a lot.

However the owner told me that I would have to turn the gasoline handle upside down while filling the tank, otherwise i would spill gasoline.

Sure enough he was right, but I cannot find any visible reason why it does not let the gas in without having some of it come out.
And I have to dispense it at 1/10 gal speed, faster creates a spill to.

Can somebody help the newbie out, and possibly turn me on to a link for a repair if possible?

Also my shifting indicator is not working, the owner mentioned adjusting the cable, and to be careful, is there any tread on this, I hate to mess it up.

TIA

Max