Not much will fit under a 14" wheel really.
That said, the 4 spot caliper on the front of a 240 is really only a good set of pads, rotors and some improved cooling away from being VERY VERY good.
But, if you do want more there are some decent options out there as far as decent aftermarket are concerned that you can make fit. I used Mazda RX7 series IV calipers on mine with Volvo 740T rotors, with decent lines and ducted backing plates.
The Mazda caliper is quite good, it is readily available, replacement parts are inexpensive, it's all aluminium in construction so is lighter and dissipates heat beat. Pistons are also very close in size to the Volvo 240 caliper pistons, therefore there is no need to worry much about brake bias changes.
