Personally? I'd not "modify" a russian motor like that, I'd stick it on a classic 1940's cruiser & ride it as-is, or sell it if I wanted to play the hop-up game - it's what the "china girl" engines are best for, cheap & disposable thus perfect for modification & experimentation.
I'd lose the china & shiftkit in a heartbeat if I had a russian for this;
I agree. The china motor is much better for cheap replaceable experimentation. The russian engines are out of production and are growing harder to find. I'd think long and hard before modding one. You could easily get four to five times the price of a china kit for a good running russian engine depending on condition and rarity.