No way will they bolt right up.. !!!! While the bolt pattern is the same, the diameter of the skirts on the bottom of the 800 cylinders are 2 mm's too big in diameter.. the 800 jug will not drop into a 600HO or 700 block.. You first have to open the bore in the top of the upper crankcase the 2 mm diameter first. And that is just the start of the issues.dyna-tek racing said:800 jugs will bolt right up as far as the pattern and case but the piston will not make it to the top of the cyl becuase the differnt stroke of the 600 and 700, you have to shave the bottom of the cyl's off to make up the difference or deck the tops depending on the application or usage,done a few 800 bottoms with 600ho jugs to make stroker 600 motors but not to many 600 bottoms with 800 jugs ,those are hard to dial in.