9" rear drum wheel cylinder bore diameters

Greetings from Australia, FABOs.

I have a '65 Valiant, and I have done some Aussie redneckery to fit 75 seried Landcruiser 4 pot calipers to the front. These are marvellous, but they have a smaller swept area than factory single piston calipers, so my rears lock up too early now. Before I go down the proportioning valve path, I was looking into what different wheel cylinders are available for our cars, and I found these smaller bore units that seem to be fitted to bigger engine early cars. Most of the factory cylinder bores are .813", but these are .594.

More Information for RAYBESTOS WC34876

Can anyone confirm these are legit, and this isn't just a misprint? I have also been on the Raybestos site, and they too concur with the .594 bore dia. Just wanted to double check with you more learned guys on this, before I order them.

Cheers,

Rob