[Jac Mac]

Some food for thought:
1. If you do a crossover setup [ 180° as per GT40 ] on a Cobra remember much of the GT40 sound is due to the two tailpipes being close together, In the Cobra instance if thay are some distance apart each tailpipe will sound like a single 4cyl exhaust, perhaps not what your after.

2. I built a system for a SBF powered TVR that races out here in NZ, each bank of headers go into a 'flat' collector as per any normal V8 setup & then the tailpipes from each collector go into one large flowmaster type muffler [ dual inlet/single outlet - self built ] and then one large oval tailpipe exiting out the rear, so its effectively an 8 into 1.... The exhaust note on this thing sounds quite 'sophisticated' for want of a better term & has an absolutely delicious howl once it reachs ~ 4/5000RPM, yet complies with the 95db limit on the tracks we race it at. There were several Cobras @ the Hampton Downs meeting in NZ earlier this year & all of those guys were very interested as to whether a system like this could be fitted to their own cars.

3. I have built several similar systems for road cars now, incl one 351c Tunnel Rammed Ford Falcon, on a quiet sunday or saturday afternoon I can pick the exhaust note of that car anywhere in town & the owner just loves getting it up in the RPM range where it starts to boogie sound wise.