[blykins]

I've spun the 4.100" stroke engines up over 6500 without issue. Where would I put the limit? If the rotating assembly is good quality, then I wouldn't have an issue at all with a 6500-7000 rpm setup. As you say, the Dart blocks use a 2.750" main diameter and the cranks use a SBC rod journal (2.100), so the bearing diameters lend themselves to some higher rpm action. At a 4.125-4.155 bore and a 4.100 stroke, it's still an oversquare situation and these engines make a ton of horsepower and torque both.

As stated earlier, it just comes down to budget. I wouldn't bat an eyelash at 500-550hp on a production Windsor block, so it just comes down to how much money you want to throw at a particular combination.