Morgo you are wrong, and sorry my friend but these are not chevy cranks, that thing of the wide vs narrow ridge mark does not apply on every manufacturer and is not a rule of thumb buddy,
I know for sure cuz i have been working with these T engines since the 80's also we use to stroke em using Y engine cranks but they fail to work cuz they wernt forged cranks so back with the T cranks we went, and there is NO WAY IN HELL a cast crank no matter how good it is can survive on a boosted 500+ hp enviroment without exploding like a fried hot dog.
If you want there is a way to find out that my grandfather showed me to find out what crank is forged and what crank is cast and this one is the resonance way, yeap and ol school way to identified cast cranks vs forged ones and is as easy as hiting the crank with a common hand wrench while having it standing on the flywheel base without touching it, and if it makes a long bell like sound is forged but if it makes a dry thump sound is cast, try it and you will be amazed of how wrong you where before buddy.
Good luck,
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