I'm assuming you have a PPG mixing bank and are tinting it until you hit your target. If not, send an original sample to the color lab and they will match it and do a sprayout. They do it all the time. They will fax the formula to you or your jobber. I sometimes do this with Glasurit when painting bikes because not all formulas are available from all manufacturers. Bike formulas are not readily held with consistency in the industry. The lab may even have the formula in their system. Lemans Blue is not available in DBC either, only DBU and lacquer from my jobber. I have to call the PPG or Glasurit(BASF) lab. Shooting today's lacquer is your choice if you want to rigidly adhere to originality. And if you clear it you just strayed. Keep in mind if you lined up 50 cars in 67 they would not be identical. So who's color is correct?