Unfortunately, the car won't be worth as much as the job done right.
We used to do 20-30 motors a year. Now we do about 6. This is because of two things: with cars running cleaner has come vastly extended engine life and the cost to restore has reached the value at half-life.
I was in Aruba two weeks ago and was proudly shown a pair of early Corvettes (56 and 63) that would easily be worth 30-40k each.... after a 50-60k restoration..
BTW most of the motors we do are for cars that aren't worth the cost of the repair (240D - 300SD). Usually it is for someone who is the original owner or bought when very new and has driven it for more than 100k.
Bosch Master, ASE Master, L1
33 years MB technician