There's a world of difference between CT70s and ANY collector car marque. The only absolutely essential parts needed to potentially build a concours-correct/100-point CT70 are the frame & LH engine case with the "correct" S/N...and even that's not set in stone, there is no factory registry for indisputable documentation. A full-on custom CT is likely to retain little, in terms of original parts, beyond the frame, gas tank, seat pan and folding bar clamp; orphaned frames, that will never be worth much, are easy enough to source in solid condition, cheap, too. That's partially why I built mine on ST70 frames. You don't get to ride right from the get-go. It's still a blank canvas. Just as form follows function, title follows VIN. Aside from initial acquisition cost, the biggest differences are likely to be regulatory hoops you may have to jump through and obtaining insurance. Pre `74 bikes face few regulations. Specialty insurers have few qualms over agreed value coverage on a Honda, the same might not be true with an obscure moniker, such as "Dirt Dobber". You might want to try titling & insuring the bike before investing your time & money into customizing it. The heartbreak you prevent could be your own
The best Q/C I've seen on any clone bike was on the last of the Jinchengs. They came closest to replicating Honda details but vanished from the US market as others popped out of the woodwork with cheaper versions. Rupps & Dirt Dobbers were decal-engineered versions of the same bike; not quite as well made as the JC versions, but better than what's followed in the ensuing race-to-the-bottom price war. As I recall, your rear hub is a reasonably faithful copy of the OE design, with the 4 rubber isolators & steel C-clip ring land cast into the hub. They predate the failure-prone (doomed?) all-aluminum copies used with the tubeless, one-piece, rims. Stay away from the newest rear hub copy, mainly marketed under the Skyteam moniker, that uses 4-bolts to retain the sprocket. Those OEM rubber pieces are there for a reason.
Circa 2001, JC bikes cost more at dealer wholesale than most clones do, at retail, in 2010. I wouldn't go so far as to say that production numbers, alone, account for the quality of the finished products. Look at what's happened to raw material costs, alone, since then. It's more a matter of the varied ways the bikes have been built to ever-lower costs, something had to give.