I had a 1998
Ibiza TDI and modified it many years ago. Best money I ever spent on a car! Then I repeated the excercise with a little bit more besides on a 2000 model TDI Beezer. Only
problem I can think of is the suspension which is not very good when the engine is standard, it will be woeful when the engine is modified. Just needs some decent gas shock absorbers really, plus maybe some second hand Cupra springs if you don't want to run to a full suspension kit, anti roll bars would be the icing on the cake. Makes a hell of a difference to the 90 bhp engine, believe me!