Well shyster is corrected except for the "full floater rear end" part. Linking means you get rid of the leaf springs you have and use triangulated tube links from the frame to the rear axle. You are able to achieve more suspension travel (if you get rid of the back frame and tube it all) and it can generally handle the big whoops or hits better if the shocks are valved right. Its not always the best route as it takes lots of time to set them up correctly and are usually expensive. Now in your case it would be way overkill for what you need. A good set of deaver leaf springs would be great for you and that front end.
Now as for teh full foating rear end, that deals with the axles only. There are genreally two types of rear ends (well three if you count independent), Full floating and Semi floating. A semi floating rear end puts the vehicles weight on the axles using bearing at the outer ends of the axle tubes and also uses C-clips in the differential to keep the axles from coming out. the problem here is if the C-clip breaks, your axle is going to come out fo the rear end. Also they have a tendancy to have the outer bearing wear into the axle and eat through the axle under hard abuse or break the axle. Your ranger has a semi floating rear end.
A full floating rear end has the axle "floating" and does not support the vehicles weight. Instead the outer hubs where the wheel is bolted too has two bearing and ahuge nut to hold pressure on them like the wheel bearing on the front of a two wheel drive truck but the axle has an outer flange that bolts to the hub and goes through the wheel bearing never touching them but "Floating" so to speak in between the wheel bearings. these are stronger and usually found under 1 ton trucks and some 3/4 tons or high end rear ends for off road trucks. If an axle breaks, your wheel wont come flying out and you can continue to drive on it (unless your an open differential and no 4wd).