Look on e-bay for some “block hugger” headers for a SB Chevrolet engine. . Access to the spark plugs appear to be easy and they appear to tuck in close to the block for suspension and frame clearances. And..... they are cheap! The block hugger headers come with kits consisting of the exhaust pipe adapters, gaskets, etc.
I will buy and install block hugger headers to use on my 1962 Chevrolet Bel Air and dispose of the OE cast iron “rams Horn” manifolds. Then I can run the ignition wire over the valve covers instead of under the manifolds. I like to change spark plugs about every 3,000 to 4,000 miles or every time I change the oil and filter.
I use a long 2 quart capacity WIX oil filter which may present a header or exhaust pipe clearance problem on the driver’s side.