Yeah - I've heard that from vendors too - but... looking at the engine they're identical in castings, literally identical. I've seen variances in castings with other engine kits, the head's cooling fins in particular but the Grubee and the Flying Horse don't even have the littlest deviation that I can find...
The thing with the Grubees is they include all sorts of extra stuff with the kit... (mounts, extra gaskets, hardware, bigger tank etc.) I almost wonder if that's the difference? That it's a "better kit" like the vendor says - but the engine itself is the same, it's just the Flying Horse kit doesn't have those extra bits? I dunno as I've not gotten the Flying Horse kit, just checked out a buddy's.
Still - I suspect they may be the same... I'd defo get a Flying Horse if it was cheaper, particularly as just an engine and not a full kit.
I'm all ears if anyone's got any more info tho