If the engine has been overheated it is almost never "just a head gasket"
When an engine is overheated a lot of other parts can be damaged. If it has been severely overheated at high speed, then the engine may not be worth repairing. There can be hidden collateral damage that could come back later to bite you.
Problem & Solution
Common among these chassis:
Classic Sedans
Ponton
R107
W108 W109
W110 W111 W112 Sedan
W111 W112 Coupe
W113
W114
W115
W116
W123
W124
W126
R129
W140
W201
W202
W208
W210
W211
W220
Watch Kent's youtube video in which he will explain what potential problems you may run into. One of them is making sure the cylinder head has not been badly warped. He will also show you an example of an engine that only needed a head gasket.
To inspect your engine after removing the head you will need an accurate machinist straight edge to help you determine the condition of the head and cylinder block. See related products for the straight edge Kent recommends.