Well, I cannot change the car, because I have it and it is already under restoration!
But I believe it will work, because I had another XR7 1974 powered by a stock 460 V8, and it was much more heavier than this 73,
and with a little work in the engine (429 cylinder heads, Holley 750, new camshaft, higher compression, MSD, etc), harder suspension, with a C6 transmission
on 2.56 rear ratio, 255/50-16 tires, I was able to drive it around 140MPH steady! This was in 1995! That 460 had no more than 300HP.
That car wasn't so fast in 1/4 mile (15.2 @ 103 MPH), but was excellent on highway. I didn't believe myself the potential that car had !
Now, I know a AMG Mercedes have millions of dollars on research, but the only thing it has in its favor is aerodynamics. The E63 engine has 525HP,
the torque is 465 ft-lb @ 5200RPM, It weighs 3883Lbs and a rear ratio of 2.65 and .82 on sixth gear (the gear when comes the top speed).
My rear ratio is 3.25, the AOD or 6R80/140 has .67 on the last gear, so the final gear ratio will be closer to AMG.
My engine (Ford Crate Stroker Big Block) will be a lot more powerful than the Mercedes 6.2.
The engine manufacturer claims it has 750HP @ 6000RPM and torque around 700 ft-lb @ 4500RPM, and it has a fair idle and a good vacuum !
The stock 1973 Cougar (with the cast iron 351C) weighs 300lbs less than Mercedes.
With the new engine, surely it will be lighter (Aluminum intake manifold and cylinder heads + the hooker headers, lighter than the original exhaust manifold)
So, the only thing agaisnt me is aerodynamics! I'm making a hard brake and suspension improvment too!
(12.88" front and 12.19" rear Wilwood disc brakes), 285/40-18 Z rated tires, front and rear sway bars, etc.
I know is too hard to beat a car with a company like Mercedes-Benz behind it.
But anyway, I'm making my car and soon I'll see what happens !!
Even if I won't beat the E63, I will have an interesting toy on hands!
Thanks!