I have a set on the convertible. My castings were pretty nice looking. No issues with the valve guides. As mentioned, the port to seat transition is not great from a performance point, but nothing that would be an issue other than port flow. In my application, I did not use the springs and retainers, because I went hydraulic roller cam. I did use the springs and retainers later on a friends 440 with 906 heads, and the Mopar 292/0.509" cam.
I wanted a but better flow, so did some mild porting on the heads and a performance valve job. I think after the work, they flowed around the 290 cfm advertised. We did not check the out of the box flow, but I think I read another post where is is around 260-270 cfm out of the box?