Some newbie questions about 4-link spring selection
 

I have a '49 Ford F1 pickup. I just finished installing a Jaguar IFS and a 460/C6. Now I am starting on the rear suspension and would love some advice.
I really only have experience with leaf springs but I am going with a custom triangulated 4-link for this truck. I am using a Ford 9".

My main question is how do I measure to make sure I am ordering the correct coilovers? There is a TCI kit with everything designed for my truck, but I want to design it myself so I actually understand what I am working with.

I assume I set the rear end up on jack stand and lower the truck until it is at ride height. But then how do I know how much my springs will be compressed at ride height? Do I just raise the truck 3" above ride height (assuming I will buy 3" travel coilovers) then measure the distance between shock mounts and buy shocks with this maximum length and 3" travel? That doesn't seem right, because I do not know how far the springs will compress at ride height...

Hopefully someone understands my rambling and can point me in the right direction. Any and all related advice is highly appreciated. Thanks!!

Most suspension manufacturers lay their coilovers over(not vertical) so the ratio from wheel travel to shock travel is NOT 1:1. You need to figure out how much travel you desire then you can start planning what shock will fit your needs and how you want to mount them. Most shock manufacturers will tell you where ride height should be for their design. Once you know the sprung weight sitting on the axle then springs can be chosen based on some fairly simple math.

I've been down the custom road myself and I will tell you from experience that with limited knowledge you are opening up a can of worms. You're better off starting with a "kit" designed for your truck and keep the customizing to a minimum. For instance, buy a parallel 4-link with coilovers, mounts hardware etc designed for your truck but have them delete the upper bars and panhard/track bar. Then just cobble together some upper bars and mounts.

-J