Believe me I know a project car is a project of love unless you buy it right. I spent the last 10 years finding old rusting classics and bring them back to life. Some were restored back to original others I just got them runing and sold them. Here is just some in the last years.
Today the classic car market is in the dumper which means it's a buyers market. Even at the the olds has a low end retail of $24,000. More than many fully restored classics.
So which is easier to in stall. Hellion twin turbo or Whipple? I'm looking to get in the 800 HP range. At that will I need to also mod the drive line and bottom end?
I wouldn't buy the project car...it'll be a money pit.
I wouldn't want 800hp on tap in my daily either. I'd get some suspension upgrades, good set of wheels/tires...and spend some of that money on a few track days this season(HPDE, not drag).
Then I'd take the rest and go on a nice vacation. Maybe even with the Mustang. Plan a road trip. Go drive some fun roads around the country, stop at some good restaurants. Create memories.
Avoid the project car unless you have a lot more money and a lot of time. If the GT is your daily driver I'd wait until the 2017 GT350s come out and trade it in. Use that $9K to help offset the cost. Hell even if it's not your daily driver I'd still use that money to upgrade to a better car. A supercharger or turbo setup would be nice for some more power but I'd personally rather have the better overall driving experience.
Either way it sounds like you're in a good position to have some fun!
To answer your question, yes, you'll need more than just the whipple. Half shafts. And if it's a manual you may want an upgraded clutch. For the whipple itself, 74 pound injectors and 132mm throttle body. Maybe some suspension upgrades.
Search the forum for whipple You'll find lots of info.
And I say upgrade the stang.
Pass on the 442...especially if you're not an Olds guy. It will takes big bucks to do it right.
And it's not super collectible.
Anyway, I recently faced a very similar situation regarding the purchase/modification/restoration of a '68 Mustang GT Fastback with either a 390 or a 408-427 351W stroker. The day I received the VIN for the '16, a received a text from Chris Agee, owner of Chris Agee RestoRacing here in Georgia. He had located a very good '68 for me to check out
What a dilemma!!
Owning a '68 was always my automotive dream!
Since I do not have the mechanical aptitude/knowledge or skill set to maintain a 50 year old vintage/restomodded automobile, I decided to purchase a new car with a warranty that I know will always start everyday that I want to drive and enjoy it.
That was the right decision for me.
My budget for the '68 was significantly much greater than $9000.00.
Dump some of your cash in to your Mustang and take a great vacation.
Consider all of your resources to help make the best decision.
I would either invest that money, save it for a rainy day, or go on a nice vacation out of the country. The project car will just be an endless money pit. If you want something fast, just save the money and buy something quick and reliable than a GT with a whipple. Just my 2 cents.
And then bring it to Cruisin the Coast in Biloxi MS. It is an event of antique and newer cars that have been up to 10k cars registered. Great time in October!