Does the exhaust pipe diameter need to match the header collector?

Wanting to replace the entire system with headers and new pipes. The headers I am seeing have 3" collectors and not sure if I should buy 3" pipes or if it makes a difference to go to the slightly smaller pipe. Engine is a slightly modified 350.

Thanks for the advice.

The headers will come with a reducer for 2.5" exhaust tubing. Suits 99% of the street driven cars out there. Unless your making 600HP+, leave the 3" and 4" stuff to the race cars..

All the reducer does is introduce reflected waves into your system that disrupt the scavenging. If a 2-1/2" head pipe is sufficient for your system, a 2-1/2" collector would also work better. There's no reason to have a short piece of 3" tubing in a 2-1/2" system. A mild 350 doesn't need a 3" collector.

As the above poster said, there's not a need to go crazy with a mild motor. My only additional advise is if you want it to last a long time, seriously consider coating it. It will look nicer and last longer, and reduce underhood temps.

Just a suggestion. I've used JetHot in the past, and also found local companie to coat my headers. Never regretted it.