What's the deal with...

The gist of it lies with the fact that the filler neck is at a fairly low angle. There isn't much slope from the tank to the cap. Plus the car was design with a leaded fuel pump in mind and unleaded is much thinner so auto-stop doesn't work in most pumps. This causes the fuel level to be high sometimes into the neck.

You should install a baffle in the neck like the one in the link.

An o-ringed fuel cap like the one damraider sell would likely help a good deal and it is a nice looking piece.

On the subject of laysons they have a less than stellar reputation. I personally have bought a pair of 1/4 patch panels from them. They came in about 10 days apart, explained by 1 coming straight from factory. The first to arrive was perfect and galvanized, the second to arrive wasn't stamped as good and wasn't galvanized. But from time or order to arrival was within 3 weeks for both. So I guess I had an okay experience with them.