In 1964 1/2 AMC introduced the 232, Which was a totaly modern inline, Seven main bearings, Ohv, Not like the old Rambler engine, which had five(!) mains, and was orriginally a flathead, Now the 232 spawned the 199 the Venerable 258 and the Jeep 4.0 (Check one out, the block is all but the same on the outside, guess why, AMC made the Castings), How many other Inlines can trace thier Lineage Back almost forty Years, I bet the New Chevy 4.2 cant, Ive seen the thing, and its cool I'll be the first to admit that but it has little in common with the Good ol 250.
The 4.0 is suprisingly compatible with the other 232 based Am inlines, You can put a 4.2 crank and rods into a 4.0 and presto get a 276 ci 4.5 Liter.
I would love to have one of the Jeep racing 293 inlines in my Eagle Or my Concord for that matter. That might give the 5.0 mustangs a bit of a suprise.