Ron,the 261 rod journal diameter is the same as GMC,261 rod is 6.812 inches long center to center,the rod big end is 1.245 wide.261 stroke is 3.937,stock piston compression height is 2.062.#61 has a 3.75 bore,mine likely will need at least .060 to clean up.Supposedly you can bore them safely to .110 over. I have no way to measure the deck height ( crank centerline to block deck) accurately.But with the demensions I gave above the stock type piston sits .070 below deck.And I pretty sure this block has not been milled in the past
Canepa Twin,the 261 block deck is about .500 thick.I measured a #010 350 block and it was about .550.I know it's two different engines and the 261 has 18 head bolts with blind thred holes in the block.I just don't know if cutting the block .060 is the best way out,but it's the easiest.Also the only available head gaskets for the 216 are .005 compressed and the sometimes available .038.And by zero deck I do mean actually about .005 below deck.I'm no pro builder but I have assembled a few engines needing mock ups to check clearances and then do more machine work if necessary.
And with all this zero decking business the final compression ratio will be 9-1 with a .060 bore and flat top pistons.
