I think that is basically right, except i think both could be had with or without an engine.
The Starfire is, I think, the older design and looks different than the Skyhawk. The Starfire looks like an "8" on its side wit the small part of the "8" at the engine PTO and the large part of the "8" at the output shaft. See the first picture below.
the Skyhawk is symetrical in size. See the second picture. I can confirm that the Skyhawk has ball bearing on both sides of the intermediate and output gears in the gearbox. I have one open on my workbench. I have not seen inside the Starfire.
I don't know that the Starfire is being imported anymore- I think the Skyhawk has superceded it, but some may be available. I have heard that the Starfires are pretty loud as were the early Skyhawks. Supposedly the current crop of Skyhawks are quiet- mine is supposed to be one- but I have not installed it yet- perhaps this weekend.
kidding...mechanically it transfers power from the crankshaft to the jackshaft (by means of a single assembly) then on back to the rear sprocket.
the gearbox, imo, is over-engineered...all the assembly does is replace the old-school torque-convertor arrangement. however, it does allow for a true "neutral"...maybe it's only real benefit. again, opinion only.
that's about all i can say because i only have pictures and general experience to work with as of yet...someday i may be able to give an "exploded view" of it's real-time performance, until then i'll have to glean what i can from the 4-stroke happy-time pioneers.
I have a tendency to agree- it is well made but seems to weight almost as much as the engine itself.
You do need, however, some gear reduction and the gearbox provides it. Of course a Comet 340 torque converter would too....I have not verified the size issue though, but I will check it out....Then there will be a used Grubee Skyhawk II for sale.