The vts is the most powerful TU engine that is an easy fit to the ax, what is said in this guide also applys to the 106 gti and in most areas the new C2 16V engines.
Pretty much the same as a standard conversion as its a TU block. All the existing AX mounts can be used
Modification is required to the GT Engine mount by grinding off enough of the metal to clear the timing belt cover. Click here for pictures of modified engine mount
The 1.1 forte one fits fine without any modification however requires the forte bush to match so make sure you get the complete thing. The 1.4 Forte is the same as the AX GT mount
Any Mk2 AX Gearbox or Saxo/106 Gearbox will fit the 16v engine. The mk1 AX gearboxes will fit but some of the holes wont line up, the gearbox is also weaker so with the extra power they usually end up getting destroyed in a short amount of time.
You will need to retain the AX Gearboxes mounting plate (held on with three 13mm nuts)to work with the AX Gearbox mount. Trying to use the Saxo one puts the gearbox side too high.
It is not totally necessary to change the radiator however it does make life alot easier, the vts water pipes come close to fouling the radiator fan. Common options are
Mk1 Saxo clocks fit directly into the Mk2 AX. Mk2 Saxo clocks also fit but are a great deal more work.
Saxo clocks are digital speedo drive which replaces the cable found on most ax's. To upgrade to a digital speed drive you need to replace the cable sender in the gearbox with the digital type, run wires to provide power to it and a new wire upto the clocks.
Note: On AX GT clocks the revcounter will not work with the saxo vts engine.
With the Mk1 AX you can remove the existing rev counter and fit a 52mm one into the clocks with a bit of cutting and wedging.