Inliners International Forums General Discussion Truck Talk update - 1970 c-10 w/ 292ci

You want each of the 'head pipes' 2". The 'tail pipes' can be 1 1/2".

Running headers into a single pipe defeats the purpose, so stay with the duals (unconnected) as planned.

Mufflers are everywhere, so just "shop around". There's plenty of time.