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Spigots are the holes the cylinders go into. The 5R case you have will have smaller spigots than a 7R from 74-77. You would have to have the spigots bored out on your case. A 7R case from 73 will have the smaller spigots (these are for 2.4 engines)
Windage mods are case mods to improve airflow inside the case. It is supposed to increase the HP of the engine. It involves grinding away at areas in the case that restrict airflow behind the pistons. In my case the builder ground away too much material near the spigot of the number 4 cylinder and the case cracked where the headstud attaches.
74-77 cases will work. I like 74 cases because those engines ran cooler (less smog equipment) and 77 cases because they had dilivar lower case studs (less stress on case).
You have alot of reading to do in order to make an informed decision on your engine. I'd start with Waynes book and Bruce Anderson's 911 performance handbook.
-Andy
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72 Carrera RS replica, Spec 911 racer
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