The #3 main bearing on a 216 is wider than the 235. It's the thrust bearing that controls fore-aft movement of the crankshaft. I have installed a full pressure 235 crankshaft into a 216 by widening the thrust face width of the 235 crank, and eliminated the Babbit bearing rods, but that also requires a different length connecting rod, or a piston with a shorter compression height. A piston for a Buick/Land Rover 215 V8 with the insert bearing 235 rods makes that conversion work, and the displacement of a stock bore 216 engine ends up at 224 cubic inches. It would be possible to narrow the #3 bearing web of the 216 and use an unmodified 235 crank with the late model 235 main bearings.
An Ebay seller called "Spark Surplus" has .050" undersize 216 main bearings. It would be possible to grind your crankshaft a little smaller and use them, but be forewarned that they're a bunch of donkeyholes to deal with!
Jerry
