I used to have a Mk2 16v GTI. It was a great car, much more fun than the Mk3 16v I had.
Never had a problem with the Mk2's 1.8 16v engine (even after 155k miles), my only problem with it was rust in the floor which needed welding for the MOT. So as said, when looking at Mk2s check the condition of the shell, everything else can be replaced.
Swapping a 2.0 16v engine into a Mk2 from a Mk3 GTI is a common upgrade and relatively easy.
Even if you're not doing the engine swap, the 1.8 16v engine is decent and with brake and suspension upgrades can be a fun car on the track.
As for doors, I liked my 3 door Mk2, but I did miss having the back doors, but if it's only a toy and you don't need it to be practical, then 3doors is fine.
