Tony ,
the answer to this question is simple

MORE THAN IT WOULD BE WORTH ! Loads of people go down this road to give it the large , once youre £20k into it and its still not finished the shine soon comes off it . If youre seriously thinking about it then you must buy someone elses mistake , a project thats nearly there or a kit of parts, theres always a deal out there . To prep a shell to cope with this would cost more than a half sensible Sapphire roadcar , a properly machined block is a grand plus , etc.. etc..
Been there seen it done it , got the receipts
regards
tony