This is a great page telling you tons of stuff about 4-link. It deals with more drag style stuff but 4x4 builders can use it too http://srd.yahoo.com/goo/4-link Susp...-_bar_tips.htm
There is also this one http://www.customclassic.com/kustomkorner/techtip6.htm
And last but not least there is the whole thing on the 4-link suspensions on Monster Trucks on Truck World.com http://truckworld.com/Monster-Trucks...ter-tech1.html
I am building a Pull Truck (Truck&Tractor Pulling) right now. Anyway, my rear suspension is 2ton leaf springs because I don't want it to move at all but the front suspension is getting a straight 4-link with a panhard bar and coil-overs. The reason I am doing this in the front is to get as much axle drop as I can for when the front starts to lift off the ground. I am also going to running a huge sway bar to keep both tires planted to the track if one wants to lift. I can only run a max of 30" bars(links) but that is more than enough for what I want. On a mud racer I don't think I would go much over 40" unless you want them to bed. Also if you read thru those links I posted you will see that links that are parallel and drop down to the axle instead of just going straight will give you alot more tire plant there for giving you traction!!!
Hope that helps...Ryan
93 GMC Yukon
Chevy SuperStock 4x4 Truck Puller
Great Lakes Truck & Tractor Pulling Association