Go to a truck stop or a IFA store and ask them if you can way your car.
Last time i did it, it cost me $25
Mine tilted the scales at 3760 with me and a 1/2 tank of fuel(E body) ordered the 3800 pound springs. had them on for over 15 years now.
my first attempt to make my own SS spring was to brake open a A body spring pack. added 2 leafs to the right side and one to the left side.
Gained no lift, but made it vary stiff. i drove it this way for a while as the stiff spring keep the wheel well from rubbing on the rear tires side wall.
When i installed the SS springs, I thought i had switched brands, and was riding in a caddy!:D