In no particular order.
300 Ford 6
Toy 22R
"Maybe" more durable, 258 AMC/IH I6
The small outside dimension, versatile, durable & longest running engine format ever, small block Chevy. 45 years.
Surprised it was mentioned, but I've seen 100k H/D Evos. 100K, nothing for a modern engine they say, but it's a lot for a 2 cyl. air cooled unit, a lot.
I'm not a luddite, but my wares might indicate otherwise as I have a last year Small block Chevy & a last year H/D Evo.
