engine block supplier

I have been looking into the engine build for my car lately and have talked to a reputable engine shop and they said that for the 427 stroker kit to be dependably floggable my best bet would be to go aftermarket block. since he is the builder i want to use and he made very good points i have been lookin at the avaliable blocks. I knew there were aluminum blocks avaliable out there based on the specs of a Windsor engine so i looked into it out of curiostity. I am now thinking that would be a cool way to go (read: i am young and dumb with too much money haha ) but have come across a delima, being the good shopper my mom always said i should be i began searching for more than just Dart as a supplier, and found Man O' War Blocks, they appear to be quality blocks with extra reinforcements and such in thier designs. Now comes my question, which would you say, in your opinion is the better buy? the MOW block is about 500 or so cheaper... or even more if i opt for the un finished block and have it bored and blueprinted on my on... ideas? this will be a purchase a little while down the road i am just tryin to get my plans straight for now. thanks for helpin!

brianj5600~ i am shooting for somewhere above 550 naturally aspirated (ditched my supercharger idea), but its not the power that the builder is having an issue building in that block, its the rotational mass of the 427 stroke set up... he refuses to build anything over a 408 on a stock block.

Wicked65~ thanks for those suppliers, but i have my builder set and he and i prefer to start with a bare block and let him handle it all, less chances for a miscue... also these blocks can be bought from the manufactures prepped, meaning all machine work done and cam bearings installed as well as freeze plugs and such where all you have have to do is start the build with install of your internals...

96 DOHC Cobra~ as far as i know they are seperate intites, if some one knows for sure other wise let me know!

So is the gain in the handling of the 100 and some odd pounds worth the 4 extra grand for the aluminum block or should i save the cash and go with an cast iron design?

brianj5600~ i agree it is alot, and although right now 4k is about 2 weeks of work this job is finite so only gonna have that for about 4 more months... thanks for all yalls help! i think i will stick with iron haha unless someone has an aluminum one just layin around they wanna give me or sell me cheap! haha