I have a 1990 JDM b16a In my civic, Can I buy a timing belt and water pump for a USDM 99-00 SI? Or what would be compatible with my engine.

I'm also looking to replace my alternator, Will the SI's also work?

 

Timing belt and water pump will be the same.

Alternator will bolt up but the wiring will depend on what year car you have it in.

 

It's in a 94 CX, so should I get an alternator for a Del sol?

 

Yep.