I have Hedman 66001 on my 454. They have 2" primaries with a 3" collector. The ground clearance is good and I have very good access to my spark plugs and header bolts, however the clearance around my AGR Power Steering gearbox was very poor. It basically didn't fit. I had to ding the driver's side headers in 3 separate places to work around the box itself and the pitman arm. That was very frustrating. I also wrapped 2 of the primaries in a heat wrap to protect the steering box due to how close they run to the box. So there are some pro's and con's about these headers, especially if you have a power steering gearbox. There are pics of these headers on my website.
The Lemons are good. Probably the tightest fitting headers I have had to install..... 1/8" in some spots. Here are my race headers with 2 1/4" tubes and a 4" slip collector. I did have to notch my stock motor mount rubber flanges to get them to fit though.
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69 SS396 Camaro Coupe, 4link, 12bolt posi, Speedtech LCA and UCA's, Hotchkis 2" drop springs and sway bar, Ridetech triple remote resevoir coilovers, Bilsteins, Wilwood 6 piston front/4 piston rear, Magnaflow stainless exhaust, Lemons Headers, Comp rollers/p-rods/cam, Fikse 18x8.5 and 18x10