You were talking about cast pulleys? I was talking about the stamped steel ones cracking. Sorry if I misled you.

Yes, the part number I posted is for 1967-68 3 groove cast pulleys used with short water pump configuration. As far as I can come up with from research, they will work for 1965-66 also, but not correct part number.

I didn't know you were talking about a cast pulley. Maybe you could use a billet aluminum pulley and paint it cast iron gray. Mine is stamped steel. I have access to lots of CNC equipment so I might make a plate to go inside mine.

That would be cool to reinforce yours.
I found a billet pulley on-line last night in Black, but it doesn't seem to exist anymore. I should call the manufacturer and ask.

Well you all scared me enough to do something about it.

Very nice, Freddie. Maybe you can market that...:dunno:

Save your dust up and get an oem one....the gm pieces are not much more than the repo unlike the 291ab

3869978 is the correct original part number for all 65 Z16's (which all had PS), for all 66 L78's (regardless of whether the car had PS or not - if the car doesn't have PS then the third groove is just empty - don't ask me why they didn't use a 2-groove pulley), and for 67 L78's with PS.

Had exactly the same situation. Can't understand the disclaimer considering the original application is for 425 and 450hp cars, although looking the other posts seems to answer that question. I ended up getting the same pulley from Heartbeat.....without the disclaimer. There appears to be Chinesium and American made versions available but identical in appearance. I do have an original but it looks like it has been repaired as per the descriptions above regarding durability, so I opted not to use it.
Sounds like there is an opportunity for someone to offer a more suitable product.
In the meantime, won't be revving my 427 L72 to 7K rpm

I see I never followed up on this. I did call the manufacturer/distributor and the grooves are standard depth, so mostly a stock replacement, or dress up part.