Same set up here,mk1 Escort racing. I got Koni in Oxsford 07759438510,just a touch machining top side and got a adjustable insert,+ all ready platform for 2 1/4 springs.
Well good on 350lbs springs,lapping Brans 48.1 indy....250 lbs 21/4 Koni on rear 1050kgs weight.Plenty caster you need !!