wanting to boost an LS
 

I have a 2000 Silverado Z71 with a 5.3 230k miles. I want to put a turbo on it and use as a daily driver. Thinking I should get a newer motor and trans ill probably go with a 5.3 or 6.0, 6.2 if I run across a good deal and ill go with the 6 speed gm offers. I've done a little research and want to go with a turbo that has a wide boost range such as VGT or twin scroll. I have 2 main questions first what size turbo should I go with so I get good performance and still keep things economical? second is the crossover exhaust pipe required on a single turbo setup?

I'd boost the motor that's in there now; you can always get another one if you grenade it (or build a new motor while you're driving around at lower boost on the stock motor).

Yes, you'll need a crossover pipe. A lot of the 5.3 builds use GT45 turbos if you aren't after crazy amounts of boost. What are your power goals?

I want it to be kind of a sleeper enough power to surprise people about enough to beat a stock GT mustang or something of that nature but I'll also be pulling with this truck from time to time so I want the wide range of boost

Would I have to boost the octane (more than pump gas) if I only go with a 8 to 10lb boost?

I've seen them run in this boost range on 93 octane with no trouble, as long as you have a good tune.

A Garret GT45 (or the no-name Chinese clones if you're on a shoestring budget) would be reasonable if maybe on the big side.