The 911's aren't hard because they already have CIS systems from 74 and up. Just a matter of yanking all the old CIS stuff off the intakes and making adaptors for the fuel injectors, build some fuel rails, and bold a throttle body on the intake.
Might be able to use the intakes off a 911 on a t4 if you could build an adaptor to get rid of the angle from the intake ports, probably cheaper to start from scratch though.
http://forums.pelicanparts.com/showt...0&pagenumber=6