New to Mopar
Welcome to FABO. You're gonna have fun here.
Our club (Inland Mopars Car Club) built a '68 Valiant with a 400cid big block as our charity project car last year and used both the RMS front and rear suspension. I'd say both are well worth the money depending on what your goals are.
Our Valiant was intended as more of a street handler than a strip terror and the finished product handled like a new Corvette. I can't speak for strip traction as we never took it down a timed quarter mile. I'd check with 'AbodyJoe' and get his reaction as I believe he's got both the front and rear setup on his Dart.
One thing for sure, the AlterKtion front suspension will give you tons of room for headers and the oil pan.
I'm not sure on how limited you may be on wheel/tire width using the StreetLynx rear suspension setup.
Good luck with your project and make sure to keep including pics as you progress.
Here's a pic of our clubs finished '68 Valiant.