Which Bilstein rear shock... 871's or 872's

As the title suggests, just sorting the rear of my Mk1 escort weekend fast road/occasional track car.
Im going to have a standard (but height reset quiet a bit lower 3" abouts) leaf setup, and a modified watts type linkage (replacing the existing leafs, pan hard and sway bar setup). Also as my Mk1 is a early year model which uses a shock bracket, i have a later Mk2 rear shock mount section which i will be welding in, so i can use Mk2 type shocks (seems to be a bit easier to source decent Mk2 type shocks).
 
So I'm looking at ordering the rear Bilsteins. 
The B871's are the Group 1 shock, and the B872's are slightly softer fast road item. So I'm in two minds what to get.
The front has Bilstein struts with inserts and 225lb springs. Currently also has a 27mm sway bar, but looking to replace this with a 22mm and double width kit. Also if it effects anything I'm running 15" wheels with 195/50 semi slick type tyres (tyres could change back to normal road type later.. not sure).
 
Which shocks and which spring rate do you think would best suit? All opinions much appreciated!!