The 216 block requires some machining on the #3 main bearing web and the main cap, since the thrust faces on the 235 crankshaft are narrower, or the crankshaft thrust faces have to be machined wider to fit the 216 main bearing. I choose to machine the block, since the 1948-53 216 main bearings are almost impossible to find. You'll also need to use a piston with a shorter compression height, because the 235 crankshaft has a longer stroke than the 216, and the 216 block has 1/8" shorter deck height. Pistons for a Buick/Oldsmobile 215 cubic inch V8 can be adapted for that purpose.
The 235 crankshaft IS NOT a drop-in fit. It requires some very accurate machining and a willingness to think outside the box. I've been making "non-standard" parts fit in places they're not supposed to go for over 60 years, and won a bunch of oval track races in the process. The crankshaft conversion, along with a .060" overbore and the Buick pistons, makes a "216" a 235 with pressurized connecting rods, while the engine keeps its "original" appearance. Ray Charles could "see" a regular 235 dropped into a place where a 216 once was.
It's also possible to alter the stroke on the 235 crankshaft to make a 216 into a pressure-lubed 258 cubic inch, a 235 becomes a 270 with the same crankshaft, and a 261 goes to 300 cubic inches. Those conversions take a LOT of machine work and parts from about 4 different engines. Drop me a PM and I can give you the details on some of those conversions.
Jerry
