But Chansey has 105 Spc in RBY. If I follow your logic, RBY Blissey would have:
Spc: 75 (down from 135 because its HP is its highest stat)
Now compare to RBY Chansey:
It sounds like nonsense to give its evolved form a lower Spc. Evolved forms should follow the same Special trend than their pre-evolutions if the latter were in RBY.
On-topic, let's see if Tangrowth can have some usage here...
Spc: 110 (because Tangela had 100 Spc in RBY and ended with 100/40 in later gens)
With much better Attack and HP stats than Tangela, Tangrowth can now go mixed.
RBY Tangrowth is quite hard to destroy with these insane defensive stats. Swords Dance + Bind will remove a lot of health from its opponents. Mega Drain is for recovery and STAB. Stun Spore and Sleep Powder will ease your sweeping (read: annoying) prowess. But if you feel lucky, you can try Hyper Beam when your opponent is low on health.
I know it wouldn't be that good due to being outclassed by a ton of things (Slaking, Persian, etc.) but Furret really wishes it had RBY mechanics.
Always-crit STAB Slash is awesome, and Amnesia is always good with Furret's movepool, though 45 special hurts badly... It's not like it would be that competitive but for Furret's standards it's surprisingly good!
Also Lanturn is pretty cool:
You could fit Agility or Rest somewhere in there too if you want. Good typing and movepool with Amnesia and decent bulk. Might be let down a bit by low Speed though.
Yeah, this set is destruction. You take Special hits like nothing and retaliate with Psychic, Ice Beam and Thunderbolt for unresisted coverage, and Hyper Beam to finish off Pokemon. Stats except HP and Defense are godly, so make sure you abuse that.