with 160vc I've found that I can overexpose even 2-3 stops and still get a good, printable negative. Albeit, VERY flat(compared with normal 160vc), with pretty blocked up highlights...
most of the time I rate it at box speed, unless my subject has super high contrast, say in strong sunlight with hard shadows. I then expose(putting the shadows on Zone 3/3.5), and reduce development generally 1/4-3/4 stop.
I'm now shooting color films like I would b/w. Zone system for color so to speak.
my vote for a really nice replacement for Reala 120 would be either Fuji's 160S(rated at 100, or even 80) or 160vc(rated at 160, or 125 for a little more punch). the 160S has a little more saturation than Kodak's 160NC, which is a really nice film, but a little more 'normal' in color palette.
personal testing is your friend in this regard though. I would suggest starting to test films immediately, and find results that give you what YOU want.
we all have different opinions on the best replacement, but film is cheap, and your time is not. I hated wasting time testing my film and developing time combination, but now that I have that down pat, I am getting results that are TOTALLY predictable, just like with b/w.
if you take your film to a lab, it might be a little harder due to chemistry fluctuations(if the lab isn't too consistent, and doesn't monitor their chemistry)
best of luck though! but believe me, spend some money, test all the emulsions that you can get your hands on, even if you think it won't get you results you like, then compare them against each other. preferably, shooting in a situation allowing you the freedom to burn through a few rolls(landscape).
-Dan