Pay particular attention to oil pressure, if it's truely a 216. These motors lubed many key bearings with splash oiling only. If you oil pressure at speed is around 10-15 PSI, this is a splash system. Anything over about 50 - 55 MPH on the open road is a recipe for disaster. There are cures, but they either involve higher pressure, full engine lubrication, or different differential gears.
Replacing with a later inliner is an interesting concept, but I think you'd struggle to match a small v8 on a price / performance basis.