A buddy of mine, Colin build a 390 with the Edelbrock kit (heads, cam, intake) for less than $5000. That's $5000 for parts, machine work, everything. He sold the Shell Valley Cobra. The new owner called him a couple of months later complaining that the car only made 386 rear wheel horsepower. Colin had told him the motor should make 450 HP. Colin explain rear wheel and flywheel HP and the guy was happy.
You don't have to spend $10,000 to $15,000 to may a lot of Horse with a FE, even a 390. Just the correct part and put it together correctly.
With 386 rwhp in a Cobra, there are very few street cars that can stay with you from the red light. Now bragging about how much dyno horsepower you have is different. You have to spend the money.
Dwight