Can I supercharge my engine?

first, any engine can be supercharged. the limiting factor is teh octane rating of the fuel you are going to use. the higher the octane, the higher the compression ratio and/or the higher the boost pressure you can run.

now to specifics;

if your engine is going to be used on the street, i would limit the boost pressure to about 6-8psi, and run at least 91 octane fuel, and limit the timing advance to around 28-30 degrees total. that should keep you out of detonation problems in most driving conditions, though you might have to cut the timing back further if you live in a hot area. one thing you can add is a boost timing retard system that automatically cuts the timing back to prevent detonation as well. again though limit your total timing advance to 30 degrees or less.

for a race engine where you will be running a higher octane fuel, or alcohol, you can run more boost and/or timing as needed, though i would limit boost pressure to 10-12psi and timing to no more than 32 degrees total advance.

He should get away with a little more with the Water/Alk injection. My worry is also with the pistons and crank. I'd definitely stick to your 6-8psi and stay on top of your water/alk bottle. If you tune it for that setup and run out your going to blow a hole in a piston from detonation.