One pretty good substitute for white lead would be to go to an artists' supply store and buy a small tube of white oil paint pigment. A 2-ounce tube would be a lifetime supply unless you're building several rear ends a day. The idea is to have a thick, slow-drying or non-drying indicator dye that allows you to visually check the contact patch between gear teeth. It's also useful for checking seat width while doing a valve job.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!