What are your engine rules for the class you want to build this engine for? The machining cost for a K341, welded or unwelded would be around $500 or less. Deck, bore, valves. Internals can be pricy depending on which stroke you use. Vogel has a forged crank in 3.25" stroke that is about half of what a billet crank would cost. Depending on what you are allowed to build, one can build something really wicked with a K series. Most of what you are describing about the throttle response is true with the pulling engines. We build them for full throttle and to idle a certain way. I have found that certain carb./cam combinations work much better than others. Kohler type carbs. that have been heavily modified coming from dead idle to wide open can be really sluggish, the Mikuni type carbs. (44mm/52mm) IMO would work better. If you keep them off the idle circuit the Kohler type carbs. are not too bad, but if your engine speed bottoms out and the idle circuit kicks back in then you would have to build up the curve again. I would be really curious to see what one could do with a K341 in this area. I know how they work for us on the pulling tracks, they may work out great for racing, then again they may fall on their faces. If you do decide to build one to race, keep us informed about it. I would really like to see how it fares on the round tracks. I think your biggest enemy will be be getting rid of heat. We run ours down the track, maybe idle them a little then shut them off, they are not run for a long period of time. MWSC sells a fan than can be used on these engines that helps get rid of heat. The issue with relying on the flywheel w/fins is that it is cooling off the side of the block that runs the coolest, air and fuel while the engine is running will cool off that side considerably. Keep us informed, very interesting application.