I would have thought egg moves are a no-go, since there's no breeding in RBY.
...and there I overlooked something big. I just saw Scolipede learning Twin Needle/Pin Missle and though that it could work.
Hopefully egg moves are allowed, otherwise, Scolipede is outclassed by Persian and Ninjask (which is also interesting, since it gets Slash iirc, and with base 90 and it's godly 160 speed, those crits will hurt even without STAB). I guess EQ and Rock Slide could give it a niche, but I think Landorus is better for that even with the lower speed due to the higher attack.
EDIT: Nvm, only Gigalith was correct. All the others had shitty Special because I don't know how to check stats.
SPC: 60 (60 over 70)
Hyper Beam / Mimic
Gigalith can be considered Golem v2. He is better in almost all stats, and doesn't have a Ground-typing. He might not get Ground STAB anymore, but he trades this for a much higher offensive stat of 135, not to mention monoRock is arguably a better defensive typing than Rock / Ground. EdgeQuake for coverage, Explosion does a huge amount of damage, and Hyper Beam can be used to finish off pokemon that resist Ground if you don't want Rock Slide to miss. Mimic is also an option, although there isn't much you can do with it. Maybe a recover or something.