Upper Molding Hole Measurements.

[Jim Boy]

Good day boys and girls. I am contemplating the installation of the upper side molding on my 68 C10 Chevrolet. According to the Factory Assembly Instruction Manual all the hole measurements are based on a line on the different drawings numbered 30. I read somewhere here a while back that that number 30 is located by measuring from the ground up to the line. I got to thinking about that and in order for that to be true the truck has to be perfectly level, all the tires on all trucks would have to be the same size and the truck would have to have stock height. So to me this doesn't make sense. So what my question is and hopefully a member here will know how to arrive at that number 30 location. I have read that there are two different types, one with all holes and one kind with holes on the ends of the molding and 3M tape in the centers. Either way you still need the measurement to be correct or the moldings won't be at the right location. All help is greatly appreciated and will contribute to a good nights sleep. Stay safe eh! That's an order from above.