i have done a SOA with out changing pinion angle ( cut and turn, or c+t). i do however have a bj60 which uses a 4 cylinder diesel, and 5 speed which i think may give me more front driveshaft length. but if you use the stock sagging leafs you may be able to get away without the "C+T". lots of info if you use the search function.
how would you use the bottom spring perches with out shimming? first the perches have to be on top of the axle to do a SPRING OVER AXLE conversion, second if you did cut them off the bottom of the axle you could weld them wherever you wanted and at whatever angle, therefore removing the need for shims. however using either the lower perches or upper bolt saddles would be more time consuming and troublesome than buying a set of new ones at the 4x4 store or the dodge dealer.
i would suggest looking into the faq (frequently asked questions) section at the top of the 60 section, and using the search function to dig up some good reading material from other members who have already been through this. lots of good info here, just got to dig a little.