1970 318 duster exhaust question???

I have a quick question to run by you guys. I have a 70 duster 318 3 speed that is bone stock and I want to add dual exhaust. I have been looking at having an exhaust guy near me do it up in 2in. with the stock chrome tips, but then I found TTI's 2.5in kit with the turn downs. I want the sleeper ok and don't really want the chrome tips coming out the back so I was thinking of doing the TTI option. Do you guys think the 2.5 exhaust with an H pipe and stock manifolds will reduce the back pressure too much and actually hurt my performance on my little 318 2 barrel? Like I said its stock with manifolds and a single exhaust right now. Looking for a better sound not really any huge performance gains, but the TTI system is so nice with the stock appearing turndowns.