Yea but with no rake in the suspension it's going to bottom out quick with little load in the bed.
400# is nothing, and in older trucks with more factory rake it wasn't as much of an issue even with similar suspension components.
I'd look into the prices of air bag systems also.
I'd say you could find some leveling kits for under 400 clams.
When you said you were loaded I was expecting much more weight.
I haul more than 400 lbs in nails every day.
just busting balls
http://www.airliftcompany.com/shop/59565/
Nice simple kit with remote fill / deflate chuck.
Or upgrade later and add on board compressor.
You are right. I was way off with 400# estimate
Here's a pic of my truck with 160 bags of Rubberific mulch when I did my house landscaping (that's maybe 1,250# in the bed). It wasn't so bad squat-wise considering it is leveled.
I am thinking I was really overloaded with the trailer at the tongue. Oh well.
Trailer had 2x canon imagerunner 7095, 150 lcds, 50 printers, 50 desktop scanners, 125 phones, cables from everything so it had a lot of weight... the 7095 units were sitting in the very front of the trailer.
10mpg towing from VA Beach to GA at approx 65mph. Love my truck. Probably will go for a WD hitch.