I have been looking at getting a set of K1 rods, but which should I go with. They have a standard rod, light weight, and supreme light weight rod. I always like to make the rotating assembly as light as possible, but still want it to be held up. I don’t really see an rpm or hp rating on the different rods they offer. Will be building a 370 engine to run with a procharger.

 

The real stress on a rod is the transition from exhaust stroke to intake the weight of the piston stopping and changing direction and vacuum it is pulling place it under a lot of tension.
Saw someone do the math once for an LT1 and a stock piston at 6500rpm was almost 3200lbs of tension on the rod a 68 gram lighter piston dropped the tension figure by over 400lbs.

This is why you don't see a lot of hp/rpm ratings on parts because it is all interrelated.

Building a blown motor I would find a shop you trust and then trust them, talk to them about what they want to do stay informed but trust them.