916sp run 34/30 valves. the cylinder spigot holes in the cases are 2mm bigger. the only desmoquattro engines with different stud spacing are the 996 - 996/st4s/s4r.

you can make any of this work, but you'd be far better off with a st4s or s4r engine.

you'd need to swap the 916sp timing gears and primary drive cover for some single pick up 916/748/st2 early alt ones. then it shoud be fine