I've just installed b74 on v20z using jumpstart. Some problems with autonegotiation with Cisco switch but beside this it installed without any problems. It booted with 64bit kernel :) I'll do some tests in coming days. Thanks to Tomasz for giving me this v20z for tests if only for a week :)
We will try to install Linux on a second disk tomorrow. One of sysadmins had a problem with Debian and he will try with Suse tomorrow.