The +1 indicates the pinion depth is .001" back from the "nominal" depth which was standard for factory assemblies. Check the new pinion gear to see if there's a corresponding +/- dimension, and change the thickness of the shim pack between the rear pinion bearing and the gear to compensate for manufacturing tolerances.
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!