Hi, man i already went down this road once...learn from my mistakes bud, the prob with a 366 is this: #1 the bores, the bores are very small and there isnt very much room to bore them until you hit the water jacket, now you can always sleeve them for the low price of 900-1100 dollars for all 8 cyl to be sleeved, by then you could have bought a merlin block thats already bored out to whatever you want and theres plenty of room to sleeve it if ever needed. Now, thats just one problem, Next problem: #2
The clearance needed for a crank thats worth a shit, if you put a crank in there with 4.250" stroke its gonna hit so your gonna need to clearance the block right? no problem right? wrong, its gonna hit the water jacket if you clearance it that far because the block was cast for a 3.075" stroke (or close to that) crank. Other wise if you want one i have one rotting here you can have the piece o' $hit. Other than that they make damn fine door stop Let me know if you can get one to work out because if you could that would be awesome because thats a heavy duty block that would make a massive motor instead of an eye sore in my car port....later,Joe