Hi folks. I got a mock up kit from GP headers today for my blown 292. These will be 3 into 1 times 2. What are the pro's and con's for running them all the way down or stopping them in the engine compartment? Sorry if this is a dumb question. Thanks for any advice. They will be Stainless TIG welded. These go in my 53 Chevy half ton pickup.

Longer pipes smooth out exhaust pulses, scavenge better, and produce more torque.

The math I've seen for ~5200rpm L6 says that the primary pipes ideally are in the 20" range before their first merge.

Should I try to keep them all the same length?

Not if it requires using a small radius bend anywhere near the exhaust port.
Your primary size should be based on expected horsepower, not what a NA 292 uses.

It's going to be pretty tight around the blower plenum and the rear exhaust port may be behind the firewall a little. Gaerte Racing Engines are building the engine and they are in touch with GP for specs. With the serpentine balancer, oil pump drive and blower pulley I need 7" in front of the crank snout. The 292 is 3" longer than the 235 I think. Also my radiator is almost 8" thick with the electric fan. I can move it forward a little. I had a mid-shift kit put on the TKO 600. I will be mocking up next week. Hope I don't end up with a COE.