every "GT" was a one-off car built to the specs of the intended use & the driver
there is no "standard spec sheet"
iirc there were at least 3 engine versions - depending on the competition venue intent
what do exist are the FIA Homologation specs
http://www.914world.com/bbs2/index.php?showtopic=321849> (Competition)
Spare Parts List, 914/6 March 1970 Porsche Nr. 6024.14,
and >
Information Regarding Porsche Vehicles Used for Sports Purposes 1st edition (german )
and > Info. . . . . Sports Purposes
2nd edition to 1972_english (.pdf) 4890.20-200-03-72
i believe i posted links to those long ago - or just google 'em
AND then there are at least a dozen books, each with some tidbits of 'originality" unseen in any other publication (all of which i acquired over the yrs)
finally - spend some hours here
http://www.914world.com/bbs2/index.php?showforum=44