you could always take the necessary percautions letting it go through a heat cycle which is letting your car get all the way to operating temp. and driving around then let it cool off and then get it to operating temp. again. i put 80 miles on my 4.10s b4 i gave it hell.
oh boy, you guys are gonna make me get up on my soap box.
there is a definite break in period for gears, as there is for any new piece of machinery or assembly where metal contacts metal. when the gears are first mated together, there will be metal shavings caused from the gears rubbing each other, no matter how good the installer sets the measurements. the gears also need to be heat cycled, which is getting the gears up to operating temps, then letting them cool, then repeating once or twice more. this is because the metal, when hot, is a bit more maleable and can better conform itself to it's new operating pattern and contact points. i would change out the fluid after about 1k miles to get all the metal shavings out, then feel free to wail on it.
Last time I checked up on breaking in a 4-stroke engine, there was a guy that tested break in's. His results were that it's crucial to go heavy on the car within the FIRST 20 MILES...
He has done this on over 300 vehicles, and his results were the same. If he followed the manufacture break in periods, the pistons didn't seat properly. However, when he was heavy, they seated perfect and were clean as a whistle when he pulled them out.