Depends on how far you want to go...if I had a GT...get the transmission...or at least drop the pan and put in Dexron VI fluid, a new filter, and a Trans-Go Shift Kit...which makes the car shift way faster and is a lot easier on the hard parts/internals of your 4T65E tranny...
Mods...I would do em like this...
Custom Fenderwell Intake (make your own for like $50)
180* T-Stat
Autolite 606 Spark Plugs
MSD 8.5mm Spark Plug Wires or PRJ 10.4mm Wires (Pricey but you never have to buy wires again FWIW
)
Front Powerlog Manifold
3" Catted Downpipe/U-Bend Delete
ZZPerformance HV3 Upper Insert
ZZPerformance Modded 1.9 Rockers...they say you can run them on stock springs but I would get some cheapy LS6 springs/retainers (90lb. vs. stock)
Ported Throttle Body (Contact Reptile on here about that...runs ya $50 I think plus a core to send him after he ports yours. He does awesome work for the money)
And all of that I say you could get for a grand or less.
Honestly...I would do a good tune last...and with all of those mods you might be able to keep the stock tranny...or at least see how far it'll take ya
I would be willing to be with a good launch and all of those mods...MAYBE a high 14 low 15.
