Here's an aluminum V8 that isn't cast of pure money...
Ford owned Rover when the 4.0 and 4.6 motor was in them. I don't know where everybody is getting their engine weights at, but this motor in stock 200 hp(about 280 ft lbs)4.6 form weights almost exactly the same as the 2.3. Accessories add weight to both, but without accessories both weight about 315 pounds(the 2.3 is actually about 10 pounds heavier). The Rover can be stroked to 5.0 and built to 350 or so for NA, but it is a bit limited in RPM(6000 max without injections of pure gold). I'm thinking a low compression torque motor with a smallish turbo(instant boost, about 15 lbs), near stock cam and forged pistons. Methanol/water injection instead of intercoolers and hide the turbo where the right rear seat used to be, boxed in and isolated from the interior, the seat back makes an excellent lid. It dresses up kind of nice, too...
Notice the Boss 302ish valve covers(stock on 3.9, like this, and all 4.0 and 4.6 models, though they have no distributors at all)and the distributor more or less in the right place? Even the exhausts are spaced nearly correctly. Technically, it's a Ford, visually it looks like a Ford(if you squint) and you won't even have to change the front springs. and they are torque monsters! Given a choice of huge low end torque and modest top end power or weak low end torque and high horsepower up high, take the torque every time(why do you think muscle cars came with truck engines?). Torque moves the car while horsepower is waiting on rpm, add a turbo to boost the top end and you have Ecoboost, the best of both worlds.
Grumpy