Regarding 40 hole hub availability...
Schwinn, at least during the early half of the 1980s, used 40 hole rear rims on their serious Touring bikes. My (slightly off topic) Voyageur came stock with Super Champion model 58 rims mated to Sansin Japanese hubs. These were (still are in the case of my bike) great hubs although seldom mentioned. They have true replaceable sealed cartridge bearings. I'm sure there were many other loaded touring bikes of the decade which were specified similarly, due to the realistic expectation of carrying extra weight on the rear wheel.
Generally speaking, the Japanese had long been fans of French touring bikes and this was once a very standard application for such wheels. So, I would not be surprised to discover that other Japanese manufacturers had also made 40 hole hubs for the purpose.
For that matter, I've been saving a pair of New-Old-Stock Campagnolo Gran Sport large flange hubs which are drilled 40 rear and 32 front. These date from the era when this was still a common and even preferred drilling - for racing bikes, as well. Perhaps it's time to check the discard bins of some older local bike shops... and begin counting the spokes on overlooked older bikes in thrift stores.
I too would certainly love to find more clincher rims with these drillings - preferably in a low profile polished alloy.
BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA