It would depend on how far from "original" you're willing to go. The 261 would be almost a drop-in fit, depending on which year of engine you can find. A 54 or early 55 261 will even have the correct water pump position, while the late 55 to 62 engines will need a relocation plate to use the 216 style high mount pump. The flywheel, clutch, and everything on back in the drive train won't change at all. If you're willing to do a bellhousing and center crossmember swap, plus some front motor mount tweaking, you could even fit a 292 in there. Have you inspected the early 235 crankshaft from the knocking engine yet? If it's still round and isn't scored, a swap to a new set of rods will put you back on the road with a simple engine rebuild. There are still plenty of reconditioned Babbit rods out there- - - -I can usually find several sets on Ebay, both standard and undersized, at pretty reasonable prices. Building a spray-oiler engine isn't terribly difficult once one gets past the "Babbit rod" mystique. Scrape-fitting the rods for a good fit and setting the oil clearnce with shims isn't rocket science-- - - -some of Dad's mechanics in the 1940's and 50's could barely read and write, but they knew how to fit rods!
Jerry
