I'm no expert, but some have posted their views:

http://www.mightyram50.net/vbulletin...ll=1#post27638
Quote Originally Posted by LSR Mike View Post
The difference between a 2.0 4G63, and a 2.4 4G64 is deck height, i.e. the cam gear is further away from the Crank. If you were to use a 2.0 cam on a 2.4 engine you would still need the longer belt of the 2.4. as fro the distributor, the FI unit has thr Crank angle sensor built into the base, you would be missing a very important signal needed for the ECU... Vacuumadvance is the least of your worries.
For those who were attracted to this thread for information about the mechanical differences of the 2.0 and 2.4, DroppedMitsu wrote:

The 2.0 head will bolt onto the 2.4 block but will also bump up the compression a bit, theres a guy on the facebook mighty max page running this setup. You could also take all the fuel injection components(and ecu/engine harness, etc) and convert the 2.0 to fuel injection. Transmissions cannot be swapped between the two as one is a narrow block and the other a wide block engine design .
A 2.4 head will bolt onto a 2.0.