So I recently got my hands on an old 420r (4 cpu's 4gb ram) and I was told I should be running solaris 8 on it as 9 would be unbearably slow and 10 is too much for the hardware.

Problem is after searching p2p networks, bit torrent and linux/unix forums and common distrobution sites I have failed to find a copy of 8. Is this hardware strong enough to run 9 if Im only running in the command line enviornment?

Its not going to be a production server or anything close, just a box to beat on while I learn solaris.

EDIT: I could have sworn I looked there and only saw 9 and 10 :/ Thanks for the correction.

Very wrong, Solaris 10 will shine on that box.

Any version of solaris will fly on that box. Again, you have 4 cpus and 4 gbs of ram. Whoever told you that, he does not know what he is talking about.