[Damien]

Have you determined if the harshness is coming from the front or rear or both? If your feeling harshness in the steering wheel you should work on the front suspension. If you can feel it through the seat you want to take a look at the rear suspension.

Your shock lengths look fine based on your measurements for both the front and rear. On my '83 I was seeing about 1" of compression travel in the front and about 2" to 2 1/2" in the rear with stock springs.

I don't have part numbers, but I have seen CPP front springs at about 1,100 lbs./in. With stock take out springs range from 650 to 800 lbs./in. The gas charged shocks will also add some spring rate to the suspension.

Once you have an idea if the harshness is coming from the front or rear, I would remove the shocks from that end of the truck and test drive. If the ride quality improves you need different shocks. If it stays the same you should look into different springs. I would start in the rear based on the information in your previous posts.