Go with Eaton. There won't be any significant price difference and by dealing direct, you have an accountable party. Talk with Tom in Eaton tech support about your requirements. They will meet your specs, original specs or make it right if they miss. As Jim says, they supply many of the aftermarket vendors. The tags get removed, so sometimes the aftermarket sells the wrong springs per application, i.e. bb or small block chevy springs into Firebird applications.

I wouldn't re-arch 40 year old springs. I believe it's a safety issue. Kind of like duct taping a parachute.