I've not had my noise verified, but it's very acceptable to me. I use both a resonator in the tunnel and a muffler at the rear. 2 1/2" pipe all the way, both in and out. I think installation is the key to ground clearance as I have no issues with steep driveways or gutters.

Resonator - https://www.magnaflow.com/products/10426-performance-muffler-magnaflow-4-round-centercenter-straight-through-performance-muffler

Muffler - https://www.magnaflow.com/products/13216-performance-muffler-magnaflow-4-x-9-oval-centeroffset-xl-multi-chamber-performance-muffler

Pictures;

 

 

Edited August 10, 20195 yr by w3wilkes

I've got 2.5" on my '72 also.  Mine won't fit up into the cut-out on the rear crossmember/differential mount and is a little low.  I saw your picture and was amazed. Then I realized it's on ramps. 

Beautiful car.

Edited August 10, 20195 yr by siteunseen