It should still work. It is a little shorter (Glennster-are you sure thats a '65 B-rear? measures more like a '63!). I believe its about as narrow as you can go with stock wheelhouses. Stroker would know better, he's got this down to a science (seriously, PM stroker)! But I know for sure the 68-70 will fit, and I'm almost positive I've heard of '65-67 being used before. At 53 1/2" its a little narrower than 65-67 B-rear spec though, it'd be worth checking with someone that knows better than I do.
If it doesn't fit, I need a rear to go in my new '71 dart project, and that's only an inch off A body spec width. I'd be happy to take the housing and axles off your hands if you can't use them. I just had a housing and axles shipped to me, its not as hard as it might seem.
The spring relocation costs an extra $175 from Dr. Diff, and makes the whole thing a bolt on gig. Its definitely not chump change, but its a ton easier than re-welding your perches. And probably cheaper if you're not doing the welding yourself. Plus it will allow some very large tires, if that fits with any part of the plan.