NOTE: The evolution items have been put in shops throughout the game. Their locations are:
Thunder, Fire, Water, and Leaf stone are in the Goldenrod Department Store
Sun, Moon, and Dusk stones are in the Ecruteak City Pokemart
Shiny stone, Metal coat, and Protector are in the Olivine City Pokemart
Razor Fang and Dragon Claw are in the Mahogany Town Souvenir shop (Both before and after clearing out Team Rocket)
Razor Claw is in the Blackthron City Pokemart
The following Pokémon have had their evolution methods changed:
Poliwhirl now evolves into Politoed by leveling up holding a king’s rock
Kadabra now evolves into Alakazam at level 36
Machoke now evolves into Machamp at level 36
Graveler now evolves into Golem at level 36
Slowpoke now evolves into Slowking by leveling up holding a king’s rock
Magneton now evolves into Magnezone by using a thunderstone
Haunter now evolves into Gengar at level 36
Onix now evolves into Steelix by leveling up holding a metal coat
Rhydon now evovles into Rhyperior by leveling up holding a protector
Seadra now evolves into Kingdra by leveling up holding a dragon scale
Scyther now evovles into Scizor by leveling up holding a metal coat
Electabuzz now evolves into Electavire by using a thunderstone
Magmar now evolves into Magmortar by using a fire stone
Eevee now evolves into Leafeon by using a leaf stone
Eevee now evolves into Glaceon by using a shiny stone
Porygon now evolves into Porygon 2 at level 26
Porygon 2 now evolves into Porygon-Z at leve 40