Protip: just install the mod and start your client/server. Watch your ForgeModLoader log (the one ending in ".0" is always the most recent). Open it with something that can search for strings and look for the word "conflict". It'll tell you the ID numbers you need to fix.
For Item ID conflicts, this error is non-fatal, meaning that you'll just see a bunch of errors to fix. For Block ID conflicts, Forge will stop and scream, so you'll have to work through those 1 at a time. Since you're adding Ars in on top of ultimate, you should change the IDs in Ars's file. Try and find ranges that FTB isn't already using to maximize your pack's compatibility and minimize its maintenance going forward.
And while you're in there, turn off the Vanilla recipes for mmmPowersuits.cfg.