There aren't many B&C caribou in any herd if you think of population stats (maybe 1:50,000 caribou). The largest caribou on record have come from the broken Mulchatna Herd and Northern AK Pen Herd, and concessions within the Katmai. The Funny River in Kenai has a few bruisers, but my point is that if you're searching for a record book caribou and will be disappointed with less than potential record book...you'll not find it in 10 days of hunting any herd, IMO.
Most great bulls score 325-375 on average, and I haven't seen a 400+ in 15 years of hard hunting, and I've seen tens of thousands of 'bou from many herds to make this claim.
You might check out Boone and Crocket LIVE. According to that resource, 26 Alaska barren-ground caribou have made the B&C Record Book since 2015. The locations range from all over the state. I'm seeing Cold Bay, the Susitna River, Little Delta, the Coleen, Styx River over in GMU 19, Rainy Pass, the Gulkana, the Fortymile, The Tonzona, the Nigu, the Etivluk, and others. Pretty much a cross-section of the state. In my experience, although these are all barren-ground caribou, there are regional distinctives as to body size. An Adak caribou, for example, has a larger body than most Nelchina Basin caribou, even though the Adak herd originated from the Nelchina Herd. Similarly, animals from the Western Arctic Herd are smaller-bodied than caribou from the Rainy Pass area. As to where the "big boys" usually come from, that will require more detailed study. They show 40 animals coming from the Talkeetna Mountains, but only six from the Shotgun Hills, over in the Mulchatna Country. There are many other locations where large bulls were shot back in the heyday of the Mulchatna Herd, to be sure, but the Shotgun Hills was one hotspot. Surprising to see so few B&C bulls from that area.
I'm afraid this is one area where there are no shortcuts. Plunk down the $50 for access, and search the B&C records online. One caveat: They don't list by GMU! So you need to know the location names before you can really chart them out. The listings are quite comprehensive, going all the way back to 1928 with an Alaska Range bull that scored 429 1/8. That one is owned by the Harvard University Museum.
HERE'S THE LINK to sign up for B&C LIVE. Note that it doesn't work with the Apple Safari browser. I'm using Firefox for that one.
Here's another look at it. This chart shows the all-time top 50 Barren Ground Caribou taken in Alaska since B&C started collecting records. This is not nearly as comprehensive as it should be to accomplish what you're trying to do, but it's a start. From this, the two top contenders are the Alaska Peninsula and GMU 17. Note that although this area is referred to at the home stomping grounds of the Mulchatna Herd, that herd has broken up into many smaller herds or have joined up with existing herds in GMU 17, 18, and likely 19. The genetics are still there.
Note that to chart the B&C data, you have to look up the location names and figure out what GMU they belong to. It's tedious work.
Read it slow; it took me a couple of hours to collect this for you!