I'm putting a 454 in a 66 Elky. Thinking about 2 1/2" exhaust all the way back. What's the experience with off the shelf headers? Clearance? Installation?

I've had three different brands of headers on my Elky. Hooker Super Comps were first. They fit pretty good and cleared everything including the steering gear. Ground clearance sucked big time and the bottom tubes showed it! The second set was custom made by Stahl Headers. They fit like a glove, cleared everything, and ground clearance was superb. The Stahls are now in the Chevelle because they were built for the engine that's now in the Chevelle. The current headers and from Doug's. They fit great, clear everything, and have good ground clearance, not as much as the Stahls, but way more than the Hookers. Total cost for them was right around $600 and they're ceramic coated. For quality "off the shelf" headers, I highly recommend Doug's.

Have Hooker 2" on the 461 in my coupe. VERY tight to the steering linkage in my car, and not much ground clearance especially with a 2" drop. Even cut the collector flanges off and used stainless band clamps to connect to the 2.5" exhaust just to gain that little bit more. Would also suggest flanges thicker than the ones Hooker uses if you can get it on another set because once they're in you don't want to hassle with exhaust leaks. I laid them into the engine bay before dropping in the motor, don't think they'd go in after the fact with all the stuff I have on the car that's also in the way (PS, PB, AC, clutch linkage, etc.). Hooker also makes a 2-1/8" set but those have one tube that has to go outside the frame rail meaning you'd have to modify the inner fenders.