[Three Peaks]

Your information says this is to be a full time track car. With that information, I would give serious thought to taking this set up to a shop that sets up race cars and let them take a look at it. A race set up can be completely different from a street set up and installation may be a different ball game.

I would put the frame right side up so you can take measurements. It will be difficult enough understanding the geometry and taking measurements with it in the standard position. Doing it with the frame upside down will be downright confusing. Once you determine what needs to be done and where all the attachment points need to be welded on, you can always turn it upside down for the welding- though I don't think you will gain much.

Also, without seeing your frame and a link to the PDF file, it is difficult to determine what would need to be done to install this rear differential properly. I live a few miles from Dutchman and I've seen these rear ends in person and they are gorgeous. But after looking at them for awhile I realized it would be nearly impossible to adapt it to a Cobra frame given the dimensions from the seats to the rear axle. There just isn't enough room for the link arms to be mounted properly in the configuration they show and still use your seat. At least on my original style frame they wouldn't.
Your milage may vary.

Bob