You’re on the right track thinking it’s a Tecumseh H25/HK25 style engine, as those Kirby-built units were commonly fitted to Scott Bonnar 33s in the 60s–70s, but without the exact model/spec number (usually stamped on the blower housing or a tag) it’s hard to guarantee exact part matches because there were multiple variations with different crank sizes, seals, and internals ; the good news is most service parts like gasket kits, seals, rings, and even
TBS bearings are still available or can be matched through generic suppliers, and items like the breather tube can still be sourced aftermarket, but for critical parts like the con rod or piston/rings you really want to confirm bore size and spec before ordering, as H25 variants differ slightly, so your best approach is to identify it visually against a parts manual or measure key components, then cross-reference—because with these engines, bearings and seals are easy, but getting the wrong internal parts can cause more trouble than it’s worth.
