These are pics of a 261 of uncertain vintage I've got sitting in my shop, with what appears to be the standard 3-hole midship mount bosses. I remember swapping a 283 into a 58 Chevy 2-door sedan that had come stock with a 235, and using the same side mount brackets for the V-8, but that was LOTS of years ago!

http://www.hunt101.com/data/500/261_block_004.jpg

http://www.hunt101.com/data/500/261_block_002.jpg

58 was the first year the passenger cars went to the 3-point mounts, two in the middle of the engine, one at the trans tailshaft, so I'm pretty sure at least the later-model 235's would have had a similar provision for attaching mounts. Don't know about yours, though!
Jerry

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