Exhaust installed on my 63.5. Got the car back yesterday, and this is an industrial strength install! 2 1/2 inch to the 3-chamber Flowmasters, 2 1/4 the rest of the way. Still don't know how it sounds because I haven't had time to get it running.
Where's the "H" pipe, you ask........oops.........they "forgot." Don't know what I'll do there, but for the moment just basking in the glory of getting this far!