Check out the R33 GTR S2/S3 steering wheels, nicer than the S1 wheels. They fit and work.
Don't think the R34 GTR airbag will work with the R33 GTR, but i could be wrong. S15 i have no idea.
Most people just pull the bulb out of the speedo cluster. Pull out your cluster, and check the bulb. If it doesn't have one, plug one in, if it does check to make sure it's not blown, if it's not blown then I dunno sorry