I finally found a decent-sized anvil locally through Craigslist, a Fisher.
I had been getting by using this old Fisher, it's pretty banged up, but it's gotten the job done so far Since it was so rounded I had a local machinist mill the face flat. The rebound on it is about 90%...
Here's the new one, about 250 lbs I think, great rebound (90%) but I haven't found any markings showing the weight, just the "5" on the end. Any ideas? I tried it last night and I love it, hope it hasn't caused me to be bitten by the anvil bug!
Thanks for looking...