[cscobra]

Nothing wrong at all with a 390 block. In stock form, it has the same stroke as a 427. For easier and higher revs, as well as better durability when you're not revving it, a shorter stroke (390/427) with lower piston speeds is a better choice than a longer stroke (428 and/or stroker kit on any engine) with its inherently higher piston speeds. Any of these engines will have far more power (especially torque) than can be realistically used on the street, and plenty of power for racing, so why not enhance reliability, durability, and longer engine life if you can?

As far as originality goes, the 390 and 428 blocks are externally identical. The 428 block was installed on far more Cobras than was the 427. Remember, the first couple of experimental FE-block Cobras even used 390 blocks (albeit aluminum). So again, no problem using a 390.

Remember also to not use a carburetor that is too big for the engine. Holley's website has a calculator to help you determine the size that would be best for your needs.

Frankly, I hope no one here takes my advice! That way, 390 blocks will continue to be cheap (and relatively plentiful) for guys like me!