Years ago when I rebuilt my '55 235, was told by the machinist that 0.060" over is the safe limit. Still the case?
No, and it never has been the case. Your machinist had his head firmly inserted into a very dark and stinky place. I've seen untold numbers of stovebolts running many thousands of miles with an 80 overbore, and some race engines with 125 over (1/8") pistons for a fairly short time, producing far more horsepower than a street engine. To install a 1/8" wall sleeve, it's necessary to bore the block 1/4" oversize, hopefully without hitting water. I'm pretty sure boring and honing the block big enough for a snug slip fit for a flanged sleeve that doesn't need a press fit to stay in place won't be much of an issue.
I got started down this rabbit hole while researching parts for the 261 engine I'm working on, the one I'm hoping to build with a 24 valve, dual overhead cam, cross flow cylinder head. That one will have a steel adapter plate bolted to the top of the block, one which also retains a set of flanged sleeves that project slightly above the surface of the block. That's a pretty imaginative pipe dream right now, but it's beginning to look doable, with some creative machining and a little bit of luck.
Jerry
