From experience I would strongly recommend that you are buying a real Cobra Jet block and not a truck block. Also, check the serial numbers on the crank and be sure you actually have a 428 crank. If you go to pick it up pull off a main cap and check the crank and bearing, also check a rod bearing. Find out what machine shop did the work. Was it line bored and honed, decked and surfaced, magnafluxed, was new cam bearing installed.
http://www.428cobrajet.com/id-block.html
You're spending a lot of money so be sure you know what you are buying. Sorry to be so pesamistic but burn me once......
Good luck.
Clois
People trying to sell something can tell you anything so have your facts together when you go to pick it up or look at it. Here is some more info you may want to consider: