Pro Fab Performance is usually busy building really fast Mustangs like Don Lamana’s X275 car and Tim Hafke’s True Street Fox GT. The full-race part of Pro Fab’s business keeps them plenty busy, but the shop also has time to build some wicked street terrors, as well.

A sanitary-looking single turbo 331 lives under the stock hood, and at the moment kicks out 420-rwhp on 6 pounds of boost. More is available, obviously, but that power will come later down the road.

Case in point–Tim Hafke’s better half Amy wanted to get in on the fun with her own Fox Mustang. Therefore, Pro Fab went to work on the car, installing a stock block 331 with AFR 165cc heads and an Edelbrock intake. Tim and Amy put the engine together before the rest of the combination was installed in the car.

The driveline consists of a Champion Racing Transmissions 4R70W transmission and converter designed to make the most of the car’s Borg-Warner S300 66mm single turbo. The combo made 420-rwhp on 6 pounds of boost and pump gas.

In testing, the car recently ran a 7.20 in the eighth-mile at that power level–on pump gas to boot.

The Fox Mustang’s red interior isn’t a crowd favorite, but or Hafke it works. We’re also told both the radio and the cigarette lighter works. It is a street car, ya know.

The combo would be good for more power with more boost, but with a stock block there’s not a ton of room there without worrying about breakage, so they capped the boost level. Generally speaking, a stock block is good up to around 600-rwhp before reliability issues start creeping in.

This combination is just to get the car warmed up, anyway. In preparation for real power, and to keep Hafke safe, Pro Fab also welded in a 10-point roll cage.

Once Amy gets tired of this power level, we’re sure more will be in store, but not too much. Her car can’t be faster than husband Tim’s GT, after all.