Thank god you opted for mostly real not Ghetto go-fast crap! 4.9 ..? you need to work on that. Too much more Hp/torque and you'll need a gearbox and clutch upgrade, then rear pinion upgrade. Rear gear alone will get you over 1/2 second out of the hole but you'll lose top end. I never liked drag cars much but muscle is cool is you;re into straight line running. Go to the web and check out Ariel Motors and look at the specs on the Atom 2. It will chew up and spit out all but even the quickest crotch rockets and humiliate Enzo's, Lambo's, Hemi Chargers, Mustang Gt's, Corvettes etc. etc. and runs a 2 liter Honda rig and running gear. Power to weight is about 600 hp. per ton. Now THAT's a fast car. $40K isn't a scary sticker either for a car that takes a crap on a million dollar Ferrari!
Julene, my youngest kid (you met Jana briefly) has a friend with a stock 06 'stang GT that's aweful damn spooky fast too. Good Lord! I could get in alot of trouble with that toy! Glad I'm grown up now and "most" of that speed stuff is in my memory. Oh, and that I lived thru it! You'll have let me thrash... er um... drive yours some time and show you how it's done. LOL