ditch the interlock side cover and replace it with a ball and detent side cover. keep your steel shift forks and nip off the ends so they work in the ball and detent cover. Interlock = junk and problems.
True the ball and detent is much better, but to call the interlock junk I have a hard time understanding, why you are telling the guy to junk what he has and spend money which appears to be clutch related.
This individual is trying to bring back a car that has sit for 15 years.
It is not like a trailer queen, the guy just wants parts to work and drive his car.