I replaced the catback on my cobra and am in the process of mocking up the irs tailpipes on my 89. With the anti roll bar, coilovers, and stock fuel tank going under the axle is about the only way i can get tail pipes on it.
My company used Generac without issue for a few years. We switched to cummins because there wasn't any local support from Generac. It sounds like a non issue for you though if you had a rep come out and quote it.
Looking for a good set of DB/9 hole heads. They don't have to have cams,lifters/lash adjusters, or rockers. I will take complete if necessary though. Thanks.