OK, I only installed Solaris 8 for Intel once and that was quite a while back... I don't remember I had major problem though.
Anyway, I'll give it a try when I have time (probably this weekend). One other thing is, which Maintenance Update you are using? The lastest is MU5 (or 4/01?). I heard that 4/01 changed a lot from the original Solaris 8.
Also, if you can catch the full path in "Cannot mount root on /pci@0,0/... fstype ufs " that'll be great 'cause then we can determine where it failed. I can't remember (or maybe never knew before) where it mounts the root fs during install (I'd assume it should be a ram disk, like any of the free unices).
Also, just out of curious, which version of solaris exam you are going to take? Or is it not SCSA at all? (I mean it could be java exam.) What I mean is that if you want to take solaris 7, better think about it again since solaris 9 beta is going to be out soon :-).