Looks like an early 1950s l-head. Seller describes it as diesel, but I doubt that.
https://miami.craigslist.org/pbc/for/d/boca-raton-antic-hobort-willys-welder/7259633410.html
“It is a willys diesel motor needs a 6 volt battery to start needs some cleaning and paint photos will tell all .Someone told me it is the motor that the army uses for jeeps I would think it would have to be dependable.”