Date registered: Jan 2013
Vehicle: 90 350SDL, 98 S420, 97 SL500, 94 S420, past owner of W108/W112/W114/W123/W124/W126/W140 & W220 cars
Location: Tampa, FL
Mentioned: 8 Post(s)
Quoted: 604 Post(s)
The early 170s were very basic, as this one is, which can be a good thing for a restorer.
What you have to ask yourself is are you restoring it for a driver, or to resell?
You'll need access to a good machinist, interior and paint person. Much of the way you do the work will determine the cost. If you're going to farm it out, better have some very deep pockets.
There is nothing unique or collectible about this car, other than the marque and it's age. It is highly unlikely, as is true with most restorations, that the amount of time and money invested will be less than a restored model's value.
About the only way you can come out ahead on something like this is if you do most of the work yourself.
If you really want a 170, I would encourage you to save up and buy the best one you can find. Restoration can and usually is a money pit, no matter what the car.
I haven't looked lately, but last time I did models like this in very good condition were selling in the high teens and low 20s.
Just my $0.02. Good luck!