[Dino Dino Bambino]

The Bullitt originally came with only a N/A 4.6 making 315hp & 325lbft. Evidently a previous owner added the Roush supercharger. If it's the M90 unit taken directly from the 427R, it'll be developing 435hp & 400lbft.

 

[Dino Dino Bambino]

Thank you so much for giving me some facts. It seems for that year, only the 5.4L engine was factory Supercharged. I am totally not complaining as this car is way faster than I need it to be...And I like it! I just wish I had more data. I feel when it's time to change the belt, I will have difficulty finding the right fit.

A picture of your engine bay would be helpful. The air intake of the M90 starts on the front driver's side and takes a long course across the engine bay to feed the supercharger from the rear passenger side, which isn't very efficient. If your supercharger is fed from the driver's side, you may actually have the much better Roush R2300 which, in stage 1 form, was rated at 475hp & 435lbft. Stage 2 took it up to a whopping 550hp & 500lbft, which tests the limit of the stock connecting rods.

 

[Dino Dino Bambino]

This is the engine bay with the Roush on top. If you need a more closeup photo, I can send it. You will notice the air inlet to the Roush is on the passenger side.
View attachment 305561

That's definitely the M90 from the Roush 427R.
If 435hp isn't enough for you, Brenspeed provides an upgrade that'll bring it up to 490.

Brenspeed 2005-09 Mustang GT 490 R - Roush M90 Supercharger Upgrade Package

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