It depends a lot on whether you want to keep the aircon or not, If you do want to keep the aircon, about the only choice is to modify an cosworth one, be prepared for a lot of fabricating. why do you want to mod the intercooler? what power are you up to? the standard IC is good for about 325 bhp.
As Claymore says really, it depends on what power you are running and theres alot of easy fix ideas for this out there especially if you want to keep the air con. Have a look at loads of different turbo car specs and you'll be suprised on what powers different standard intercoolers can take. I mean, mine can take up 400bhp before needing a front mounted.
Also depends if you are running standard turbo or not. Most standard turbos already have an intercooler suited to that engine, and alot of standard intercoolers will take a good size turbo before needing the extra cooling.
Oh and dont forget, you wont see much gains at all fitting an intercooler, only how the car runs. And dont waste your money unless you feel that the charged air from your standard/uprated turbo is too hot by the time it reaches the engine. Scoobies are good for being able to pick up on this very easily if you have a dump valve. Just put your hand round the vent of your dumpvalve and rev the car to make the valve dump and you can feel the air temp from that.
But like I say, dont bother unless it's really needed.