I believe the fig adapaters are pressed on. So you will need to have a shop install the adapaters for you, unless you have the proper tools. The adapaters spaces the bolts just enough so that it lines up with the Is300 caliper bracket.
Not worse, just front bias. You can make them bolt up though without the adapters but you have to drill out the caliper bracket. If you're not comfortable with that then just get the adapters. And i have heard of people just beating them in and out with a punch, hammer, and vise and no special tools.
yeah they are good brakes, everyone has already gave you a answer,
the stock is300 brake calipers are good? why do you need to get supra ones? unless your boosted or doing some outrageous sort of tracking your car, then thats considerable, and guessing from your s/n do you even have a is300? lol