I was thinking of going with 3" exhaust for my new truck, but I think that may be a little big. Would 2.5 work better?

single 3" would be perfect, dual 2 1/4

Thanks.

I run a 2 into 1 with 2-1/4" from manifold to the muffler, and 2-1/2" out. Duals on a smallblock are for hotrods, not necessary for what we're doing.

When you reduce backpressure dramatically, you lose low end grunt. Keep that in mind. Big, free-flowing exhaust is for high revving engines. If this is a trail rig, or even a tow rig, you'll want that torque for taking off with a load.

Something to consider...