Thats a nice looking car.. Looks like it dosent need too much..
Resto's are all about budget... Are you going frame off?
If have a tight budget look at bodywork and paint only.
I think the Silver would look good but not as good as the Blue..
If your going frame off you have sometime to wait for color. Would suggest going to some shows to see the differing cars and color if you can.. Also look on ultimate GTO site you can look at all 66 colors and some pix of each
If you dont care about original equipment and are building for fun
My opinion or what I did
On suspension go poly bushings on all control arms and A Arms, and oversize front sway bar. Get or make rear boxed control arms and get a rear sway bar. Get extra rear frame supports.
For funner car.. save the 389 set it aside and find a 428, 421, or 455 block. Get Lightweight Forged rods Tomahawk by Pacific performance are decent priced and quality. lightweight BRC pistons forged....
Find a used set of E-Heads. 87 CC's can be found for about $1600 or a tad more. Seems expensive but worth it.
Crower 60919 camshaft
Tranny wise if you want to push pedals over the auto...I would never go for a 4 speed once I put a 5 speed Tremec in my car.. Save save and sell sell to get a tremec Is hands down the best upgrade I did on my restoration..
Rear .. If you can find a 12 bolt it would be good or a ford 9" conversion set up//
All these upgrades get into some serious bucks and it took me a long time of saving and selling to afford that route. But performance wise its a different car with that drivetrain and suspension set up
Did I mention that car looks in real good shape Do you need to replace the floors or trunk Any rust issues..
Oh yeah learn to DIY it you will save a ton of money and get dirty