Most folks don't assemble or service their car (beyond the basics) and thus have no need for a manual. What would a Nincompoop like me do with an service/assembly manual other than to use it to prop a door open. I say know your customer base.
There are 99 Cobra buyers like me for every one like DanEC.
CSX, KMP, SPF and BDR have successfully sold thousands of Cobra replicas without a manual.
ERA's, KMP's, SPF's, BDR's, etc. are all great cars, but my purchase decision and DanEC's purchase decisions were different. He's assembling an ERA and enjoys the process. I'm no DanEC. I just want my car to look and run good. Anything more than tuneups and
oil changes, I'll take my car back to an experienced shop.