I'm not sure what the advantage to inverted shocks would be. If I was going to do it I'd check with the manufacturer first.
As to your liftyou have 6" now (SPOA with stock springs and a 2" body lift.) Perfect for 33s. That is if it was regeard for the added tire height.
If you go to an arched lift spring it will cost in the articulation department , since flat springs articulate much better than arched springs when a SPOA lift is utilized...So to gain the tire size you THINK you need -----you must re spring , re gear , re shock ,
possibly re brake line , extend your drivelines , extend your track bar.......etc. etc. etc....
IMO a Samurai with 6" of lift (done right) and 33s is the perfect set up for all but the most extreme wheeling....
If you are new to the offroad seen take some advice from someone who is not new to the seen . Stick with the lift and tire size you have while working on refining your Samurai in other ways...
Here is a picture of mine for reference. SPOA - 1" body - 1" shackle - 33x12.50x15 - long travail shocks (hydraulic)..Have fun....Boxcar...