70 dart 470 ci drag car build.

By old, I a lot older than 69. I'm taking course spline axles and stuff. I can tell you that my d60 has .050 under the race and is set to .005 backlash but I have a spicer gear in it. Richmond usually wants a lot of backlash especially if it's a pro gear. I would put .040 in it and check it.