To confirm - the CX Plus Four and Plus Six ( along with Super3) parts books are via the Morgan dealer portal. The confusion comes in around model years - there have been changes and you need to know which MY ( model year) car it is - which isn't set out by chassis number regrettably and the date of registration is not a reliable indicator. They are not in a pdf or similar format that allows for easy downloading. MMC have been very helpful with allowing dealers to publish the older ( Trad) parts books ( Cain @ wolf performance has links on his website, and Brands Hatch Morgan have them on theirs too). I would suggest contacting a dealer for specific CX info - most are very helpful.
Yes, I understand it is via the dealers portal, but it would not be rocket science to transfer the data to another format that could be made available. With reference to the MY. The chassis number must be linked to the MY, other wise it would become guess work even for Morgan to supply parts. I cant see these points as an excuse in all honesty, the BSA/Triumph group changed their thread types across their range in the late 60's and into the 70's, well before computers and .pdf existed, they did not do this at a MY change point, but rolled it out gradually, it was not a great idea, but they still managed to sort it in their paper parts books and schematics.
I have tried the dealer network for info, but this does not work well.. It depends on the dealers attitude in your area. Not all dealers are equal. I have found them reluctant to answer or no answer. I have asked the factory if a contact point for info could be set up and was told a contact is available now but only for dealers. The MMC system is presently set up to channel anything CX related through their main dealer network.. period..