first thing to lok for is the special edition plate in the engine bay - its in front of the radiator ..
it has which number it is and who was the original purchasers name on it - thats the easiest way to spot an original - if the plate hasnt been swapped from a smashed grp a
Secondly - they are water to air intercoolers , not air to air .. check for a small water top up thingy next to the intercooler - thats another quick way
the other changes are in mechanicals - stronger gearboxes and diffs , a few subtle changes here and there - and the obvious bonnet and front bumper changes
if in doubt - take down the cars vin / engine number - and call toyota direct - they SHOULD have a registry on the Grp A's
PS - i hope your frinnds prepared for the harder to get intercooler parts
A friend in QLD had a grp a 185 - the water pump for the intercooler - to replace with new cost him well in excess of 1000 dollars - just for the parts - 4 years ago ..
Overall the Grp A's are fantastic cars - but theres only a bees whisker in perfornmance differences between it and a standard GT4
The main differences come down to mechanical strength in the drivetrain - and the intercooler - Bar those - the cars are near on identical
He could save himself 5 - 10K buying a stock gt4 - and spend the extra cash on a better front mount intercooler - boost controller and suspension goodies , but then again if he wants the special edition - if left pretty mugh stock they do keep their value over the standard Gt4 ( sort of like a real GT falcon Vs's a hot XR8 comparison )