I would suggest there at Mt. Silver. The place has Pokemon that raises all the EVs. From experience, Dolphan gives the most exp. points. So if you have your Pokemon fully EVed by now, then please igbore the list below.
Pokemon and EV yields:
Larvitar and Pupitar raises attack by 1 and 2 receptively
Dolphan raises attack and defence by 1(each)
Onix, Tangela, and Graveler raises defense (Onix and Tangela by 1, Graveler by 2)
Golbat, Ponyta, Rapidash, and Sneasel raises speed (Ponyta and Sneasel by 1, Rapidash and Golbat by 2)
Phanpy and Quagsire raises HP by 1 and 2 receptively
Golduck raises SAttack by 1
Misdreavus raises SDefense by 1
Anyway, hope that I helped