The only real difference in a 235 and a 261 is the bore size. All the other 235 parts will fit- - - -crankshaft, rod and main bearings, cylinder head, etc. are the same as a 235. Pistons and connecting rods are different, but the rods can be reconditioned and reused. Getting 30 cubic inches more in a drop-in fit package is always a good thing, just from a torque standpoint. That was the reason the engine was designed for medium duty and big trucks, and there will be an even more noticeable difference when that engine goes into a pickup.
If you decide not to pull the trigger on it, I'm interested- - - -I've only got three of them stockpiled so far!
Jerry
