Kiknasp,
I own a B&B also im in upstate Ny there arent to many of us out this way. as far as the rear goes I have a 8.8 and am narrowing it this winter. (Im running 295/60/15s and have a ton of tire rub) you should be ok as far as tire rub goes if you get the backspace correct. I would check with brian.
As far as the reg goes that really depends on the state and how fussy they are. I can't speak for N.H but N.Y is a pain in the a$$ my car is titled as a 97 shelby convertible I got around all emissions by using a 289 out of a 65 mustang. They go by the date of the motor. you need to talk to some guys out there that have done it.
you'll have to take a road trip in july to the summer run in lake george I meed a few more b&b's there
Greg