I have done two ground-up restorations (on lf Fords) and a partial resto on a 635.
The first, a 65 Mustang, took 2.5 years. Figure an average of 10 hours per week, and you have 52*10*2.5=1300 hours.
Parts cost: ~$12K
The second, a 73 Bronco, was in better shape. It took 15 months, but I was putting in about 20 hours per week on it (ask my wife!)... So that's 4.3*15*20=1290
Parts cost ~$10K
On both of these I did 98% of the work myself, including paint (I did have a trans guy tweak the auto-transmissions on both cars...following my total teardown and rebuild)
Seems pretty consistent. These were nut and bolt restorations with an essentially new car emerging at the end.
My partial resto (1980 BMW 635 Euro) took about 8 months and was about 10 hours per week (344 hours), head, clean and paint engine, restore and paint engine bay redo entire interior including rebulding the heater/ac and the dash.
Including the new leather seat and door panel covers. I probably spent $3K on this project.
So, if you have limited rust and are not a concourse nut, figure on 1000 hours. If you do most of this yourself, then it will be "free".
I have 72 E9.. minor and manageable rust, needs paint, suspension refresh, interior and engine cleanup. I am figuring on $8K for the paint (not doing this one myself), $4K for the interior, and about $5K for other incidentals.. that on top of about 1000 hoursof my time....This in a clean but very tired $6K car..so the total investment wil be on the order of $23K..on the other hand, I'll have a pristine E9...
S