[83GMCK2500]

DirtyLarry, you are the man! Thank you very much for the information. Yes, I first came across the L21s in the GM Electronic Parts Catalog (that is where I started thinking it might be possible for me to get C-O-P on my L29), my research shows them to be C-O-P in 1999 & 2000, carrying the RPOs L21 & LP4. In 1998 the EPC shows, 366 (LS0) & 427 (LR0) V8s with distributors...I would presume them to be the fuelie versions of the classic tall deck BBCs.

From what I can tell I need one of the L21 cam sensors, crank sensor, and reluctor wheel. Don't remember, might need L21 timing cover. I am bundling this with an 0411 PCM swap, btw.

Looks like I'm on the hunt for some 2-year only valve covers, sweet, I love rare parts.