Ok, knowing you have done the things I have and are about 300lbs more on the nose, you will most likely want either a longer (which will be very hard to fit) or a slightly heavier spring. I worked my spring backwards and added 300lbs to the figure. Here are the measurements I came up with..
18" long spring a 260lb rate
17" 300lb rate
16" 350lb rate
I think that might be a little on the heavy side. Here are the figures adding 200lbs in:
18" long spring a 250lb rate
17" 280lb rate
16" 330lb rate
The thing to remebder is if you have a really long light spring and it sits too low for your wanted ride height, you can always put a 1-2" spring spacer up top before putting the spring in. As long as you don't induce coil bind under bump, you'll be fine and store more energy than with the shorter stiffer spring.
Quick way to figure out where you will induce coil bind, count the gaps and measure then. Multiply them together (IE 15 gaps, .1 between = 1.5") So that means you have 1.5" of spring copression before bind. You would have about double that number for wheel/tire travel due to the geometry.
So when you call Moroso tell them you are looking for a spring with roughly the above rates/lengths and a coil bind of less than 7.5"
When they give you part numbers ask these questions:
Uncompressed height
Fully compressed height (Bind height)
Rate
Then I'll work the figures again for you with the info they provided.
Order a couple of them, set them in the truck and see what ones are closest to the ride height you are looking for keeping in mind they will settle 3/4 - 1"
I did not cut anything out of mine. Just did the math to find the right spring
