Does anyone know of a any good basic 3 point harnesses that can easily be installed in an mkiv? Do I need to upgrade the seats? Are there any harnesses that will work with the factory seats and factory seat belt secure points?

well I am harping on this one.

Why exactly do you want a harness and a three point one at that?

A harness as with all safety equipment is part of a total system. IN other words a harness does you no good if you do not have a helmet on (think about what would happen in a crash). A harness also does you no good if it is not installed correctly and on a stock seat, that is not correct