If your mechanic is younger than his mid-70's, he's most likely not very experienced with the lubricating system 216 engines use. It's not terribly difficult to fix properly, but it does take a skill set that mostly went away in the 1970's or before. There's a very labor-intensive and time consuming procedure involved in getting the rods to fit the crankshaft properly and to make sure the oil squirters in the pan are aimed correctly to keep them lubricated above idle speed. A 1954 or newer 235 will be almost a drop-in swap but Ray Charles would be able to "see" the difference in the two engines.
A full rebuild on a 216 would probably cost somewhere in the ballpark of $3K or so, or possibly more, depending on whether or not the engine need to be bored, new pistons, regrind or replace the crankshaft, etc. One modification that's definitely worth the money is boring the block to 3 9/16" and installing standard size 235 aluminum pistons, bringing the displacement up to 224 cubic inches and putting less load on the rods with aluminum pistons instead of cast iron.
Jerry
