4 pots would be wasted on the rear, the money you could sell them for would probably get a new set of recon 4wd rear calipers.
The thing you would be missing is a HANDBRAKE , which is a legal and MOT requirement, and VOSA or POLICE can give you a prohibition notice for this.
As said already 4x4 calipers are by far the best and easiest thing to do.
tabetha