SO that means the old school Briggies with the exposed spinning top and side starter, around since the 50's, is a good one.
The 50s was quite a good era for enduring engine design. Ford's Windsor V8 and the Buick V6 to name a couple.
Well, nope; the alloy block/alloy cylinder bore ['KOOL BORE', in Briggs-speak] Briggs engines first came out in the early 1960's, IIRC. As did their first vertical-shaft engines. I'm sure CyberJack will know for sure.
As for '50s US engine designs, you've somehow overlooked the major classic - Chevrolet's 'small-block' V8 family, starting with the 265ci in 1955, with the legendary 283ci coming out in 1957.
And Ford's first OHV [they had made side-valve V8's since 1932] V8 was the 1954 239ci 'Y-block', also first of a family.
