It isnt a huge difference, but there will be some alterations you will have to make....
Computer, wire harness, radiator support, electic fan, all the motor accessories, have to be added or altered in some way.
you will need the different exhaust components, IC brackets, and IC, the list goes on to little things!!! Air dams and such.......
If you find a decent, running intercooled motor, you will probably spend 1000+ on just the motor alone.... Then you need the accessories and bolt ons.
I have considered the same route a few tiems, as the offer has come up in the past....but for me to go and spend all that time and money to convert over, I could just save a littel bit longer, and go buy an 86-87 T or GN, and save myself from all that work and possible errors.
In the long run, if you want to go fast, buy a hot air for 2500, sink another 5000-6000 in the hot air to get to low twelves, high elevens, with good investments and tuning.... Spend 5 grand on a good running IC car, and for another 1000 or maybe less, you could be at the exact same place with that car, as with a hot air car. If you sink 5 grand in a hot air, you know your car in and out...if yo sink 1000 in your IC car, you know your bolt ons and that is about it....
All a matter of the individual doing the work....How much money, and how fast do you want to go are the questions that have to be asked.
Good luck!!!
John