I believe I've found a way to convert a regular 235 engine block to a 261. It involves boring the block oversize and installing a flanged sleeve intended for an aluminum block 5.3L Chevy engine. Here's the sleeve dimensions- - - -which require reboring the 235 block about the same amount as installing a 1/8" wall repair sleeve in a 235.

www.jegs.com/i/Melling/689/CSL355F/10002/-1

I've ordered one sleeve from JEGS, and I've got a junk 235 block to experiment on. If that doesn't work, that same sleeve can be used to repair a scored or "worn out" cylinder on a 261 to bring it back to .030" oversize.

Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!