I'm considering doing a t-chain on one of my 78 Magnum, as the water pump needs changed.

I"m to the point of having all pump related items removed, now, from this point, what's involved, and while I'm in there, I have some keyways to alter the cam timing, as I've heard late 70's small blocks had the timing retarded, and much is gained by advancing it a couple degrees.

So how do I know which keyways to use? I'll post a picture of the package so maybe someone can tell me which one to use?