I've got 75 914 with flared fenders and a 5 lug conversion. I looking for wheels and tires just have no idea what offset I need, I would like a nice lip on the rims so I know it needs to be a negative offset just dont know how to find the off set I need. From the rotor to the edge of the fender is around 150mm so how do I find what size rims I need.

Here is the list again!

The search will give a lot of info on what others have used with the exact same application you are trying to use.

Measure to the closest point on the inside of the wheelwell, on my 75 it's about 2o'clock looking in the driver rear wheelwell, to the mounting surface of the hub. Subtract about a 1 inch for clearance. Thats the inside max. You have the outside at 150 mm. Make a cardboard cutout of the size wheel on the chart you think is the closest and see what happens or what you will need to shop for.

I hope the alignment is close before you try to get real close to either the wheelwell or the fender lip.