I start with a used block and go from there. I do not like brand new blocks as a starting as they have not been seasoned and will change shape over time.
What kind of heads are you running? Take a look at my picture page on this site.
http://www.clubcobra.com/photopost/s...0&ppuser=18529
I have a 302 on a stand that we are putting in a MGB It is good for 320 hp as it sits without NOS. Should go to 7,000rpm with out much trouble.
You could build one like that and use most of what yo have on the top if it is any good. Again I have no idea what you are running.