[Jack21]

There's a guy in our club running a Vortec on a nearly stock 5.0. Gets 22 MPG on the highway, and can smoke the tires at will. I'm running a normally aspirated 351W with the usual selection of aftermarket parts. It gets 17 MPG on the highway. Both cars are driven daily.

Typical Cobra motors are running 375 - 450 HP easily. Depending on how it's built, driven, and maintained, 100,000 miles between bottom end rebuilds should be typical.

As stated above, it doesn't make a lot of sense to re-invent the wheel, when you can buy them off-the-shelf.