We have the 7" Boosters and M/C's in stock and ready to ship....these units are commonly used on early model Chevy's and will us the GM Bolt Pattern. On your application it should be all bolt up, shouldn't have to make any modifications...I can also get you the full assemble that has the pedal and all if you need it.
http://waylayedinc.com/Store/index.php?main_page=index&cPath=29&zenid=snu7hi6l64d2k5q4ll5q30vf31