GERRY - I like the idea of the Mukuni carb, but getting one hooked to the covernor control may be interesting. The Carter carbs, which are favored for their adjustability over the non-adjustable Walbro's for the K-series have TWO methods of adjustment, the idle screw & main fuel screw. You can make other adjustments, like drilling holes on the main fuel adjusting needle, or the main fuel jet, but I'm not counting those.
Most Mukuni's have FOUR adjustments that all over-lap so you can dial them in almost perfect, main fuel & idle adjustment, swapping main fuel needles, and carb slide cut-out replacements.
On your K341 engine, unless something has been made recently, you'll find all the eccentric locking bearings are 1.000" bore, nothing with the same OD with a 1.125" bore. I'd suggest having a machine shop turn & grind the drive end of the engine down to 1.000" dia and recutting the keyway. My Dad bought a new Kohler Magnum M12 for his old 129 and it had a 1.125" crank and after over a year of looking & calling around finally pulled the new engine apart and had the crank drive end machined.
Other than that your engine plan sounds interesting.
One last comment from me about the "Rare" or "Limited Production" CC's, IH built tractors for Customer Order, and their Customers were their DEALERS. A User customer could walk in and special order a CC exactly to their liking with options, but most people, I'd guesstimate 90-95% bought what the dealer had on the sales floor. They had a Dollar amount they were willing to pay and they let that determine the size, options, and attachments they bought.
In the early days, CCO, 70/100, 71/102/122/123 production, most customers were either farmers, or people involved with farming or rural areas, because that's where IH's dealers were. And Farmers tended to be FRUGAL except where equipment choice impacted their production efficiency, and mowing the yard around the house or barns really didn't increase their productivity. As in my case, when I didn't have field work to do for Dad or neighbors, I'd mow. And a seven HP CC would mow anything I needed as long as I mowed often enough, or every week. But if there was field work to do, that came first. Between Dad & I we'd probably get the fieldwork AND mowing done.
When Dad was farming, when he got his first CC, he farmed 240 acres, with a 25 and two 45 HP tractors, and hired extra help or traded help in the spring & fall to get all the work done on time. By the time he quit farming ten yrs later, he only farmed 200 acres, with a 20, 30, 35, 45, and 100 HP tractors. The extra time we gained by being more efficient was used by ME hiring out to do fieldwork for the BTO a mile down the road running his equipment. He farmed close to 1000 acres, raised 400 head of cattle every year, and lost his full-type hired man while I worked for him, so he ALWAYS had work I could do.
IH built to a Mixed Model schedule, a certain number of each model were built every day. And the model mix was adjusted on a monthly basis. The mix closely followed the mix of the incoming orders from dealers. Current finished inventory was monitored, and considered in making the adjustments to the build mix. IH was very good most times at completing the orders for old models of low production models that were being phased out, and as demand dropped they were not afraid of discontinuing models. During the time I was at FARMALL, the 4186, 686, & Hydro 86 were discontinued. The 4186 was a tired old design very similar to the original 4100 tractor, and the 686/H86 was very similar to the 560 that started production back in 1958, and identicle to the 656 that started production in 1965. The 4186 was NOT replaced, and the 786 built from common parts with the larger tractors replaced the 686. The H86 was not replaced, but the H84 built on a chassis from Doncaster, England at LVL was capable of doing most things the H86 could do even though it was 10 HP smaller, 58 vs 69. They still built the H186 which was 105 HP if somebody needed more Hydro HP.
With IH's end customers changing from farmers looking for a mower to suburbanites looking for a small TRACTOR to do mowing, snow removal, garden work, etc. the need for larger tractors grew. The lighter, cheaper Cadet tractors were capable of mowing, in fact did a great job of mowing, but were limited in their ability to remove snow, and they were not capable of pulling ground engaging implements like tillers or moldboard plows & disks.
It would be interesting to see how production, and therefore sales of the CADET line of lawn tractors compared to the smaller HP Cub Cadets.