My last "project" was a 2000 Mustang GT (4.6 liter) with a Paxton Novi 2000. With minor mods (exhaust, chip, fuel and intake) I was able to get 394rwhp..easily more than a Viper (at the time). Even with Yoki A032Rs acceleration was traction limited. Considering what little I had to do to get that level of horsepower I think the centrifgual supercharger should be given serious consideration for anyone trying to get some easy horsepower. IF their engine is built to take the extra abuse. Turbo's can be very expensive to install... and in the case of the 40, probably all custom. I don't think it would be that hard to modifiy a Paxton or Vortech kit to a 40, although some fabrication would be needed.
I do a agree with Ron, the Supercoupe had a nice setup, .. actually Ford Motorsports did do something similar to the 4.6 with a roots setup, but it never came close to the centrifgual setups in terms of performance. But you couldn't beat if for being a compact "Factory style" setup.
One thing I LOVED about the paxton is that the power curve was very flat... it just pulled and pulled hard all the time.
-Shannon