don't know if it helps you, but check out vehicle craft online. I sent my 930 rears there and had them machined to bolt up to the stock trailing arms and the setup uses a stock turbo rotor for the rear. It is around $400 if I remember correctly. In the pic above with a closer shot of the front wheel, the little bit of caliper I see is not the 78-89 930 Brembo - maybe it has the early 77-78 930 brakes which are quite different.
I have heard of the weld-on bracket too, I suspect it is "six in one hand, half dozen in the other". Just another option... obviously if I mess up a caliper, I would have to have another machined to bolt on, but I haven't ever experienced destroying a caliper so much I couldn't rebuild it...
I don't have any really good shots of the work, but you can check out various parts of my site to see what the later Brembos look like on my 914 v8 project.
www.geocities.com/byndbad914