Just a suggestion....the GM blocks are great and you can find alot of parts but if you ever plan on reselling you should consider going with a 302 or 351 block...just as many go fast parts and it keeps it with a Ford slant...plus we won't have as much to make fun of you with
The other thing you need to consider is if the GM motor will fit and you have to worry about headers and sidepipes...could be less expensive in the long run to stay Ford as well.
Matt