Dual exhaust on Chevy Nova

69 Chevy Nova with 307 and Powerglide 2 speed. I'm putting a full dual exhaust on it for a friend soon but all I can seem to find is 2.5" systems? Does anyone know if using dual 2.5" instead of dual 2.25" or even dual 2" pipes with mufflers will kill low-end torque? I'm thinking it will still be better than its' current single exhaust.

 

I think all the bolt on kits are 2 1/2 inches. Shouldn't make much difference. I bought the Summit kit for my 74 and it went on easily.
Rick

 

Ok cool, thanks.