So how far along are you? I am contemplating a similar setup in the rear and have my eye on an e46 M3 rear. Have you placed the rear cradle under the B yet? Wondering how it fits and how much trouble the trailing arms will be. How far out will the tires be? I think it's about 4" per side unless you narrow. Thought about narrowing the rear but wasn't too sure how it could be done without fabricating the upper and lower arms and of course shortening the axles. Are you building an upper cup for the rear springs? Interesting choice of engines. I contemplated the V6 Mustang with 6-spd but in the end am settling on a 5.3l LS motor mostly because I don't know what electronics would be required to make that setup work. I've also heard the V6 and it just doesn't compare in sound to the V8. Scads of books for the LS. Looking forward to your progress. Good luck!