A friend of mine is considering selling his 9in Versailles with disk brakes and im thinking about buying it from him.
What's a fair price to offer?
Isn't that a question.
I paid $300 for the entire car I got mine out of so I also got the 351W and C4.
And a local bone yard wanted $300 for just the rear minus calipers, rotors, and shields.
It should be a bolt on part, correct?
That would depend on your definition of bolt in.
I've seen people take housings where perch distance was off by an inch or more and because they could get the perch over the spring pin (because leaves without the axle flop around) and get the hardware cinched down they saw it as a bolt in. So you may need to relocate the perches.
There is the E-Brake, I'm pretty sure the cable wouldn't be a direct swap, though I'm pretty sure you can get a cable that would be a bolt it (Not like your doing this to a Mustang II).
You may need to get a larger volume master and install (a) residual pressure valve(s).
And finally brake bias. That can be handled by resizing brake components front and/or rear or installing an adjustable proportioning valve.
And depending on your level of anality, if your going from an 8" with 2 7/8 tubes tot he 9" with 3" tubes you may want to get different spring plates. I'm not sure about this one because it's been years (decades (ouch)) since I owned the 67 and 71.