Go with the ta they can out handle and brake the gn any day and as far as power stock for stock the w02 will spank it!! The gn will become a nightmare for you if you don't know what your doing with it so stick with a w02 with a set of afr heads and a fast. Intake and a few other mods I seen those cars run very low 11's high tens with no power adders but if you get a gn you will have all the help on this forum that you need ill tell you that much
There are a lot more mods needed than that to get a LS1 car into the low 11's/high 10's. To get a LS1 car in the low 11's/high 10's N/A you would need at a minimum very good heads($1500ish),cam($600), intake($1k for a FAST with TB), headers($400), exhaust($300), custom tune(which would be in the $300-$500 range or buying the software would be the same $), clutch if 6speed or converter if auto($600), fuel system($150), injectors($350) , throttle body and suspension upgrades and even with thoses items 10's would be pretty tough and the rear would be a time bomb at that level. As far as mods go a turbo Buick will run faster dollar for dollar assuming both cars are in good condition. A few years ago I got a stock Turbo T to run 11.90's for less than $600 worth of mods on a stock car and that price included the drag tires. I am not downing LS1 cars because I own one and like it but to putting a LS1 car into the high 10's N/A is not cheap or easy. Going 10's with nitrous is a different story and can be doen for cheap but filling bottles sucks!