I'm same as 4 speed, (only read it quickly)
For the lift you are looking at, I would just go with a set of offset bushes. The caster plates will have too much caster for your application, the bolt on ones (7 degree - as in no drilling) will have way too much caster for your lift, and the drilled ones (5 degree approx - you need to drill the mount plates on the diff) are a pita fro small lifts - not worth it in my opinion. In both cases of caster plates you will need to adjust the steering stops out to limit the 'lock' you have as the tie rod will hit the bottom of the cast radius arm.
Contrary to what some may have you think you will not lose flex, provided you go with the correct urethane caster bush kit. Drop boxes are good for high lifts, but the legality and clearance is something to consider, although they do work well.
The shimmy on Patrols is a complex issue, and varies from vehicle to vehicle. Excessive caster will only add to it.
I'm goi ng back to caster bushes, in the past have had the bushes, then the caster plates, then the drop boxes, then back to the caster plates, now hunting for the right bushes.
I first changed fromt he bushes as my new coils were too high for the bushes, so on went the plates. Lost a lot of steering lock, but had no shimmy, and the caster was spot on at 2 degree pos. then the coils sagged, the mild shimmy started and found the caster at around 5 degrees pos

, so on went the drop boxes (although chaging to alloy wheels as road wheels eliminated the shimmy - but was still there with the simexs and bent rims) front end then became very neutral and back to factory settings. Then DOT didn't like the drop boxes, and the battle scarring on the boxes told the story of how they can hang up offroad, it was very hard to find an engineer that could find a legal solution, so it was out with them and back to the caster plates for a temp fix. 7 degrees pos now on the caster with the plates

and the shimmy is just waiting for an oppurtunity, the steering was terrible with no lock and very aggressive return to centre characteristics (as is the effect of caster) so out the plates came and just standard rubber bushes in at the moment.
Sorry for the long post, but this will highlight the dramas you can go through searching for 'FLEX' and fixes to the drama of a Nissan front end. Just keep it simple, fit the coils, have the caster accurately measured, then you will have the amounts in degrees you will have to correct.