I'm replacing the wiring harnesses in my 1967 GTO I've got a 400 CID with factory air. I noticed I need to know if I have ram air, high output and transistor ignition to order the engine compartment harness. How do I tell if I have those option is it by the VIN number?
You can't. You should be familiar enough with your car/GTO's in general to answer what you ask. A 1967 Service Manual is a real help for such things. Several good books on GTO's will also point out these differences.
I suggest you get the PHS documents for your car which will tell you what your car was originally ordered with from the factory. Important documents to verify your car.
Transistor Ignition was not common, points are what you most likely have unless someone had converted to electronic ignition.
HO would be evident by the large header type exhaust manifolds.
Ram Air would also be evident by the large header type exhaust manifolds and the special tub that sits on the carb and seals it to the hood - with the hood scoop being open.
Both of these options are not commonplace.
IF you decide to add aftermarket Ram Air/HO exhaust manifolds, then you may want to plan ahead for this as the engine compartment wiring to the starter is a little different.
You can also use the Google Custom Search in the upper right to search through past discussions to get a better idea of what these terms you ask of are about.