There isn't a best spread per say, because there are many kind of Pursuit Tyranitar. It'll come down to the 3 other moves usually.
Here are a few one I have seen/used:
EVs: 116 HP / 104 Atk / 32 Def / 104 Spd / 140 SAtk / 12 SDef
Naughty Nature (+Atk, -SDef)
This one has been made by Halloween and used by DracoMalfoy in a pretty famous team they made a while back. The full set is Flamethrower | HP Grass | Rock Slide | Pursuit. DracoMalfoy uses here a mix of everything because the Ttar has to check Snorlax in a pinch, outspeeds most other bulky lead Tyranitar, hits hard enough on the special side while still maintaining some bulk to check the like of Snorlax. Malfoy said about it:
EVs of this one aren't meant to defend, and that allowed me to win many lead wars against other mixed Tyranitar.
EVs: 208 HP / 252 SAtk / 48 Spd
Modest Nature (+SAtk, -Atk)
Here is one I use on a full special Tyranitar. The moveset is Fire Blast | HP Grass | Ice Beam | Pursuit. The full special Ttar are the easiest to EV: enough speed to reach a given benchmark, usually full SpAtk to deal as much damages as possible to Gengar (and maximizing your chances to KO Dugtrio with Ice Beam if you run it) and rest in bulk.
EVs: 136 HP / 28 Def / 252 SAtk / 92 Spd
Modest Nature (+SAtk, -Atk)
Once again a full Special Ttar, with a different speed benchmark and a little twist in the bulk to give more chances to survive Dugtrio's EQ. The set here runs Crunch over Ice Beam, and since Tyranitar has to pressure Snorlax as most as possible in that team, the Special Attack is maximized.
http://pastebin.com/cZX6zNVk
Finally, here are a lot of spreads for a mixed Pursuit Tyranitar running Roar. They all accomplish different things and everything's explained in the pastebin I wrote some years ago.
All in all, just run close to/max SpA on full Special Tyranitar, hit a certain benchmark in speed according to your preferences and then invest in bulk.