Just finished installing clutch and trans on my 73, so am familiar with starter ring. From what I remember, you can really only put it on one way and have all the holes align (the attachment bolt holes, as well as the offset holes that the ring alignment pins go on).... so if it's bolted up, it's pretty likely you've got the starter ring on the right way.
I learned a really tough lesson with weak batteries. There is so much voltage drop in line between the battery and starter, that your battery needs to be in tip top shape to be able to work correctly. Depending on the shape of the battery, you can get anything from just clicking to a really REALLY slow crank .... neither works well. I even had my PowerStroke jumping a bad battery .... same thing; it wouldn't turn over. Believe it or not, there's also a big voltage drop through a set of jumper cables. Try removing the battery, and jumping directly from a running car into the + battery connector in the Porsche (effectively bypassing the battery). You'll have too much voltage drop through the jumper cables/starter power line to crank the starter!?!?!? Had to see it to believe it. Upon purchase of a new battery, the starter spun like crazy and the car fired right up. This may or may not be the problem, but make sure your battery is fully charged and doesn't have a weak cell or two (local battery shop can check this).
Good luck, Doug
