Well firstly, why didn't you ask here for cage fitting advice? It's easy when you know how. You need a ratchet strap (or even a rope and a stick) to pull the hoop legs in towards each other, then it goes in very smoothly.
To answer the question.....
yes its the ballast resitor for your coil . if u use a 9v coil my advice is not to !
go for the 12v coil but it will depend on the dissy u have i think ?
Sorry to Fatmini but it's best to ignore everything in that post. It's the resistor for the dim-dip system fitted in cars built from '88 on. It is legally required in those cars (although no-one would ever notice if it was removed and I don't think it's part of the MOT) and is part of the reasion why a mk3 loom is not compatible with the systems in a mk4 car. The wiring system was completely overhauled in 1976 and systems from before and after this change are very different from each other.
Also ballasted ignition (if you do have it) is a very good thing and makes starting very much easier for no penalty at all aside from slightly more complex wiring, why would you advise against ballasted ignition? Ballast ignition is nothing to do with the dizzy, it only depends on the coil, resistor (the thick pink/white wire is the resistor) and starter solenoid to function. As long as it is installed correctly the system works well.
But all that aside, the resistor by your rad is nothing to do with the ignition, it's for the headlamps. It works in conjunction with the big pink relay under the dash.