Well, I would say that you have the PERFECT car for building. You have no rust issues, body issues, interior issues (if it is as perfect as it sounds). You need to post some pics for us. Anyone you sell the car to will most likely do the same thing you and your grandfather intend.

As far as the car being too nice to upgrade to v8 muscle, I doubt that. Almost everyone on this forum and several others has performed upgrades on their Engine and suspension. MANY of these cars are really far from stock. Common upgrades include:

Rear - 8" or 9" rear end with good gears, traction mods, springs and sway bar, performance shocks, and disk brakes

Front - All new A-arms, ball joints, tie rods, Roller spring perches, heim strut rods, poly bushings, heavier duty springs, performance shocks, sway bar, shelby drop, and more

Engine - Just about anything from big block swaps, 351c in pre-68 car, strokers, EFI swaps, Electronic Ign etc etc etc.

Transmission - 4 speed, 5 speed, 6 speed, AOD, and more

Now, if you were to sell your perfect I6 car, you would probably end up with a car that has had a few of these done to it, no by you. Different amounts of wear on each component. Perhaps rust issues so you would need to take things apart to repair rust. There are so many areas to work on with a project car, I think you would be way better off with a lot of areas that are alreay perfect so you can focus on the areas that you WANT to modify, not HAVE to.

Anyhow, post some pics so we can check it out.

 

I agree with ttony. A mint 6er is the perfect car for a v-8 build.
Front suspension and brake upgrades should be done on any 40years+ car 6 or 8. And with the money saved on metalwork and interior, you should have enough to do it right.
DO IT

 

as per your conversion plans, it is cool to have a true stock origional classic car, but as others here have stated, even if you leave it stock and sell it for some crazy money, the person who buys it is bound to convert it anyway. alot goes into the conversion as has been stated here. i'm in the process myself. you have one VERY good thing going for you, NO RUST. my 66 has quite a bit of rust and various other body work problems.

the conversion will not be easy in any way, shape or form, so don't get it twisted. be prepared to run into a few snags here and there. here's a few links to check out for some help and a few parts sites. http://www.geocities.com/MotorCity/3...to8.htm?200523 <-i6 to v8 conversion, www.mustangsplus.com , www.mustangdepot.com , www.cjponyparts.com , www.mustangsunlimited.com

i'm going down a very expensive route with my suspension conversion. i can't remember the site right now, but when i get home i'll link it for you. the front suspension is about $2500 and the rear is $4000-5000. for me, it's worth it cause i want power AND handling. i'm looking to do about 50k worth of work to the car and people think i'm crazy for it. i don't blame them but when it's done i'ma take 'em for a ride.