Is that $100 or $1000?
I highly doubt it's worth putting a few thousand into it because excellent examples of 450SELs can be found for a couple of thousand. Nice 560SELs are available for $4-5000 which puts a cap on the value of the 450s. These cars are not [yet] worth the cost of restoring them.
These are terrible cars for short trips. They require a hard freeway run from time to time to stay limber and keep the equivalent of cholesterol in check. Stay off the freeway and you might see mpg in the single digits.
83 300SD ... $950, see cars forum