if you're keen to go to a pedders dealership try the one in carlisle st, st kilda. karl (if he still owns it??) helped me heaps in getting my 1200 sorted 1st time round, and is a big fan of dattos.
as for lowering it, its pretty much the same deal as your rear leaf springs - measure from the bottom of wheel rim, not the tyre, up to the guard lip and work out how far you'd like it to come down. do this for both sides, write down your measurements, pull out the spring (pretty easy job in a thou) mark drivers/passengers sides and take it into pedders to have them reset it to how far you'd like it to be lowered.
don't go cutting rubbers or trying to fit u-bolts or other dumb stuff.
good luck