For some reason Dad always got the biggest motor available, back in the 'order-your-own' days. His company did a lot of refit line work for the Claycomo plant. He got some strange deals from Ford, who was known to bolt anything that would work together. It was the biggest whale looking 65? merc. Mom was always getting speeding tickets with her foot off the pedal. It would run 40 at idle on the flat. Could have been a 460, long time ago. I do remember somebody set a speed record with an old Tbird, 560? bored out Linc. motor. Had a girl (friend) in HS who's dad was a mechanic with a house FULL of service manuals for all makes. He told me Chevy had an alum. V8 OHV in '17, I didn't believe him so he went and got the books. Hope that stuff eventually made it to a museum someplace. Funniest front suspension I ever saw was an early (AU?) tube, hinged spindle bottom & coil spring inside the tube axle.
Anyway, finally changed the plugs on the 4runner @ 100K, did front brakes too. No complaints on certain vehicles.