Well, I had a friend of mine plug my numbers into his desktop dyno along with the 990 flow data from Stan Weiss and the cams listed above. Looks like the XM278H and the XE274H work the best. The 274 has about a 10hp and 15ft-lb advantage down low, and the 2 cross paths around 5000rpm. The XE274 peaks at 450hp@5000, but is still making 447hp@5500. The XM278 pulls a little longer and peaks at 455hp@5500.
Both make decent power down low 240/247hp and 520/505 ft-lb at 2500, so I dont think I can go wrong with either. If I had to pick one, Id likely go with the 274 for the slight power advantage everywhere but at my intended WOT, and it doesnt give much up there. Not sure if Ill end up with either- but at least I have a baseline now. Ive had good luck with Cam Research (Ford only) in the past, so Id like to find a similar outfit for the BBC... next step is to call Herbert.
Thanks again for your help, guys!