MUFFLER OPINIONS

Whose doing the work? What's your priority? Where are the tailpipes coming from ?
All that plays into the muffler length inlet and outlet sizes and offset that will fit well.
Tailpipes on '67 are bit tricky. they exist a little over from the 68-69 and hang from underneath instead from the side of the frame rail or the other way around.
TTI hangs muffler and tailpipe from the seatbelt mounts IIRC
Accurate hangs theirs from the factory mount (you can buy the factory 383 dual exhaust mount - easy install)

Since you have the mufflers. Measure and compare. No point in buying new if what you have will fit and you think you'll be happy with them. Make sure there is clearance for the driveshaft and to the floor.