The first one has an issue much bigger than looking like crap. It appears that the clutch hub spline was *welded* into the adapter. That will pretty well destroy the hardening and make the splines prone to failure.Wow, is that earlier coupler for real? I wouldn't dare sell something like that to the public, even if it's properly centred and works, aesthetically it just screams crap!
That second one I really like. Some people decry set screw hubs, though I have used them without issue, even the White Zombie used one when it ran the Kostov motor without a transmission.
I went a little different route on my clutchless VW Beetle hub. I used a Ruland CLC-18-18-F shaft coupler and had a spline insert made from the input to mainshaft coupler from a VW Bus gearbox.
