as mentioned above. $60k on a GT means that $40k is never coming back. I am trying to think of $20k in upgrades you would even want to put on the Boss 302. At that point you are buying $7k shocks and spending money on a shaker rig to get it tuned right. Its not about parts and pieces anymore. Its about developement.
At $60k you can just about buy the Boss 302R.
Try over double that... a Boss 302R is $129K.