Here is what they are not telling you....The longer the stroke, the shorter the skirt on the piston, the more critical the bore diameter is and a few other things. You want to control the piston gap to .003" ish at that level because the piston wants to shingle in the bore and whips out the cross hatch on the thrust side pretty quick..

So a shorter stroke has a longer piston skirt and is less sensitive to this issue. So in an aluminum block, I wouldn't go over a 4.5 stroke, and even then, the bores have to be real nice...Cast iron, much better. I have a 605 w/4.75 stroke, and it actually has gone faster down the track in the same car with the same internals than my aluminum Indy block did.

4.5 bore x 4.5 stroke is the most popular with the most availability....I would stay away from longer strokes that that. I have seen guys making +800hp NA on Hemi's that were 528 cubes on pump gas. so they have a lot of potential.