Hello Natalie,
a friend of mine built a Midstates/Shell Valley cobra with under the car exhaust. If you want me to contact him to get a hold of you, let me know.
I had a 428 FE in mine before the side oiler and really liked it. They are cheaper to build also. Getting say, 400 HP/TQ with not much in racing parts and a little machining is not a problem. You should be able to build one for $3,000-$4,000. I would spend more money and get the Cobra Jet heads, as the stock 428 heads need a lot of work.
Call someone like Keith Kraft or Barry that are great "FE" engine builders, they have some from stock to wild, at a good price, and will preform very well. Both also have entire motors for sale, and almost crate engines for cobras. The side oilers are expensive to build, but cool to have in a cobra.
What do you want out of a engine, mild to wild ?
How much can you spend ?
If you start out with a 390-428 and build a side oiler later, the motor mounts are the same for both engines.
