Could always buy one......even Honda can't or won't give you details that you need, like cam specs, port info and valve sizes.

Honda said the GX35 wouldn't be here until April,that just around the corner,but if a trimmer (UMK435) with the GX35 in the UK costs 309 pounds (593 usd)
I can see that engine costing well over $300 from Honda here. Even at 275 for the Superior it seems kind of high considering the Honda GX25 OHC is basicly the same engine just little smaller displacement and can be had for $175.
Honda price structure on the GX 31 and GX22 had them seperated in price by only $10. I would think the same would apply on this also.