Assuming all the IVs are 0 the maximum possible EVs are:
Sp. Atk: 64
Sp. Def: 36
This is the maximum possible EVs, they can be anywhere between this value and 0, an exact determination is impossible.
Source: I created a Lv 70 Dragonite on Pokemon Showdown, gave it 0 IVs and added EVs until its stats matched your Dragonite.