I have a similar set of forks and have done that, but with a little better success since I had instructions for it.
To get access to rebound valving You must do this:
- Look at the rebound rod where the lower part is screwed to the upper part. You will see 3 or 4 small stamped recesses in the outer part. These are there to prevent the rod unscrewing by itself (which would cause the lower tubes and front wheel to drop off !).
- Take a drill and drill the stamped holes with a slightly larger drill just to the outer surface of the inner part, not through the whole thing.
- Now take a torch (or heating gun) and carefully warm the outer part. They are glued together so You'll have to warm them quite a lot until the glue melts.
- Now unscrew the parts and there You have it: rebound valving can be easily adjusted.
They "safety" the rebound valve nut at the factory by hitting the end of the bolt so that it spreads so when You unscrewed the bolt, it broke the spreaded head off (and maby fouled the nut). So You'll have to file the rebound valve body thread and maby replace the nut. Use loctite when assembling and don't overtighten.
If You can't use the old pushrod I think You should look at **** for used rod/complete fork.
Good luck!
Dogger