For N/A engine, it is not a lot of thing to do:
Working at the bottom is typically to improve the reliability, the only place to find power is reducing the weight of the piston and the connection rod, and increase the compression ration.
Compression ratio wise: increase the compression ratio, but when it is possible, I prefer to use the stock piston, and machine the head to acheive the compression ratio I am looking for, but in this case, you need to re-adjust the cam position using adjustable pulley. Me, I don't really like forged piston except when I don't have the choice. Typically, they are heavier in weight, get too much loose between the piston and the cylinder in teh ring zone. A piston for a N/A don't have the same shape than for a turbo engine. For charged engine, they have more room for thermal expension. If you buy forged piston, try to know if they are really done for NA. If the piston have too much loose, you can create wear on the cylinder wall.
Lighter and more solid conrod are all time welcome. But in US, not a lot of K engine, mainly 2ZZ. I don't think that a lot of US supplier are doing rod for the K.
I suppose that the K crank is forged, ask for better balancing, and better shape of edge to a crankshaft specialist close to your location, and doing racing stuff. If you have a ton of money, light weight and billet made crankshaft is cool, but don't give power, only reliability if the crank is not solid enought. On the old engine, the crank oil passage was very bad designed, not it is a lot better, and I presume that the K is well done. If you have a chance to look a old Renault crank, they have only one oil hole on the conrod, just located before the TDC. On the old V8 american engine, the crank was only casted iron, with only one hole badly located. On a good crank, you have 2 holes on the crank for the connecting rod, and well located apart at 90 deg of the TDC.
Connecting rod bearing is important, you need to find the best quality, typically, an engine is broking right there, the bearing deform, and squeeze the crank, removing the oil film, and create damage.
A light flywheel is cool, but again, in US, not a lot of K engine, probably no US flywheel.
The oil pan is very very important. A good pan for curve is a pan with the bottom a lot larger than the top where it bolts to the engine base. A deep pan is good, but typically no room for. The thing is not just the oil quantity, but where it si located when you are in a curve a 1 g. At 1 g, the oil level will be at 45 degrees, and at 45 deg, do you still have oil at the pump pick-up, that's the question and the answer.
Cooling the oil is critical for the engine life.
One another thing very good to do, if the engine don't have it, it is adding oil jet spraying the piston by underneath. Not easy to do, but, probably the K engine have it.