TCI is short for
Total Cost Involved, the sell frames, custom suspension parts, and other restoration and modification parts.
A four link is a suspension system that has four bars that join to the frame and axle in four places. The norm is a parallel four link like this:
http://www.totalcostinvolved.com/productdet.cfmThe horizontal bar and forward mounts bolt/weld to the frame and the axle is welded into the perches at the other end of the rods.
A fuel cell is a type of gas tank. Typically they are mounted between the rear frame rails where the spare tire goes. Here is an example from Summit Racing:
http://store.summitracing.com/partdetail.asp?part=SUM-293215&view=1&N=700+150+-128260+Hope this helps,
Drew
