Yes, a pain. 235 pistons generally sit .015-.020 below deck with a piston compression height of 2.030. 261 piston compression height is 2.030. I have measured stock engines in the past to verify this.
I built a 261 years ago with stock pistons and the block deck cut down .050. It ran well and caused no problems.....But I don't think cutting so much off the deck is the best idea...The 261 build last year has 600 buck Ross pistons at zero deck height.The engine is very responsive with the tighter quench and actual 9-1 compression.
I checked a uncut 848 head to find 80 cc chambers,I believe a 261 head is around 90 cc's. When doing the math and with known combustion chamber volume and piston height below deck ,the GM advertised compression ratio is about .5 more than actual.
