LeeS

I have a complete NOS GM dual exhaust system I am selling, I would like to make sure I don't guide a buyer the wrong way, my assumption is it should fit 68-74 for sure, and 75-82 if the cat was removed. Am I right or wrong?
Appreciate the help.

MelWff

do you have any part numbers that could be looked up?

crawfish333

I may be wrong, but I think it makes a difference if it is automatic or manual transmission. If it for an automatic, I may be interested.

derekderek

and around 77 or 78, they removed the right side exhaust hole from the trans crossmember.

gbvette62

NO. To start with, manual trans and automatic trans systems are different, small block and big block are different, L-48 and LT-1/L-82 are different, 80-82 are different than the earlier systems, and so on.

Let's assume they're small block. Generally, 68-74 small block systems are interchangeable, except for the mufflers.

Base motors used a 2" system, while LT-1's, L-82's, etc, were 2" at the manifold, but then expanded to 2 1/2". The systems can be switched back and forth, but the hangers have to be changed, and for performance reasons, I wouldn't recommend putting a 2" system, on an LT-1 car.

69-74 2" automatic pipes are all the same, and 68-74 2 1/2" automatic pipes are all the same.

68-74 2" pipes for 4 speed cars are all the same, and the 68-74 2 1/2" 4 speed pipes are the same.

68-72 mufflers are interchangeable, but they do come in both 2" and 2 1/2", to match the pipes being used.

73 mufflers are a one year only design, and come in 2" and 2 1/2".

74 mufflers are one year only also, and also come in both 2" and 2 1/2". 74 mufflers are used on 75-79's, when doing dual exhaust conversion.

Mufflers get really screwy from 75-82, with 2", 2 1/4" and 2 1/2" variations, but the differences don't need to be covered here.

A complete 74 system, can be used to convert 75-79's to dual exhaust.

A regular dual exhaust system won't fit an 80-82, because of the design of the transmission crossmember.

If the pipes you have are NOS GM parts, there should be a part number label on the pipes, that can be used to determine exactly what you have.

So have I completely confused you now?