Heo, my rails measure outside just under 29". I measured them at the point where the rails come down from the engine compartment and curve parallel with the ground. They then appear to taper inwards until they terminate after the trans crossmember. Hope that helps!
A Jaglane - should be an interesting project! 
Well then there is plenty of space. 34inch if i have the right information, I Will have it delivered tomorrow
So i can start meassuring.
I think it can be great, vented discs,4 pistoncalipers, rpstearing ,about same tracwidth, getting rid
of shocktowers ,wheight 260lbs with pallet paid about 100USD. It unbolts from the jag as a complete unit
Dont know yet if we weld it in or bolt it on