Flat springs can't be lifted as they are at the end of their life.... Jones Spring
http://www.jones-springs.co.uk/ can bring back tired springs, improve them, replace broken leafs what ever is needed... they stock standard Cherokee and Cherokee diesel ones.... so either buy new stock springs and then shackle lift or ask them about making springs to suit your needs.
I have used Jones' a few times, they have replaced broken leafs and turned them around within 24 hours.
How high are you going? What size tyres are you aiming for? How are you lifting the front?
Would suggest staying away from AAL as you have one tough leaf and over time it weakens the others and the ride is awful, better to get a complete new leaf pack imho.
Hope this helps, Maf