FIRST POST KZ650 rear hub compatibility

Can someone tell me if there's any other differences between the 40 hole hole hub with the brake drum and the 48 hole one? I need to know if there's differences in the cush drive, sprocket carrier, brake assembly, etc. 
I'm changing the 16" rear wheel on my 1981 CSR to a 18" wheel, and I thought I could just replace the rim but that's not working since the 18" rims I could find only have 40 holes. I thought I could just replace the drum/hub part but I don't know if the brake and cush drive from the 48 hole hub will fit on the 40 hole hub. Any help is appreciated. 

MikesXS shows 18x2.15 alum rim clearance at 24 bucks

then yo need spokes for your new combination? the one they show are for a yamaha, I went to 18” used a cast wheel good luck

some parts are the same. brake panel and brake shoes. axle. you can compare other parts at Kawasaki.com or partzilla (easier). the brake panel being the same would lead me to guess that it would work. you may need the B sprocket carrier and shock damper. and might have to swap out some spacers. ... fyi. the csr is a very different motorcycle than the earlier 650s and has more in common with the 80s 750H Ltd.

1979 kz650-B3 >>  www.partzilla.com/catalog/kawasaki/motor...rear-hub-brake-chain

1981 kz650-H1 csr >>  www.partzilla.com/catalog/kawasaki/motor...ke-chain-81-82-h1-h2