1.5" isnt anything on the 240 suspension and will still be in spec on the alignment machine for camber with out adjustments...
What you are describing is bad "toe"... I did the same thing, dropped my car 1.5" and didnt get an alignment, and then proceeded to wear insides of the tires out on the front. I fixed the toe (way outta spec, and the rear didnt need a single adjustment) and its fine now, and actually wearing on the outsides (well due to 5 auto-x events so far on em plus spirited cornering and 15k or so)...
Check the alignment first as camber shouldnt be a problem. Toe will wear a tire out faster then a degree or two of camber.
Oh and one more thing make sure the upper spring mounts are facing the right way as this will also play an effect on how a tire wears on one side, as I have personally found out
Im getting camber plates / pillowballs when I go full coilovers, as with the 1.5 - 1.75" I have now its not needed...
If you want to spend some coin on something you probably dont need , HKS, cusco, tein probably jic all make nice camber / pillowball mounts.