M14x1.5, 28mm thread length. Radius seat for OEM wheels, 60 degree taper for most aftermarket wheels.
Add whatever width spacer you use to the thread length. You might not be able to buy the exact length bolt you want. Just use your head. Too little thread would be unsafe, too much might foul something.
H&R used to do an 8mm spacer with the spigot for the wheel - strictly speaking, you mean wheelcentric. Impossible any smaller.