The 235 pistons (stock) sit higher in the hole then the 261 pistons. I forget off hand exactly what the numbers were the last time I actually measured but I want to say the stock 261 piston sat anywhere between .090 and .110 in the hole, and the 235 were less at like .070-.080, something along those lines. So if you are decking a 235 by .060 and cutting he head by .030, you should be getting a higher compression ratio then the similarly machined 261.
And of course, its the case that all of this machining is due to the lack of any affordable piston for either of the motors, but especially the 261, with any kind of usable compression, and the out of date piston ring package for the 261 pistons.
