@rat3de Want vs need is the point that I am trying to make here. The core of "needs" to be classified as a dredge deck, and execute the dredge gameplan is extremely small. If the idea to establish of a core of needs then its a very small list.
If the idea is to put commonly played cards, there are others you are missing:
4 Hollow One
3+ Mana Confluence
3+ Nature's Claim
4 Mental Misstep
4 Prized Amalgam
2+ Dread Return (not just 1+)
1 Elesh Norn
1 FKZ / Kologhan
So there really aren't 39 flex cards. Its more like 20ish if you want to be strict about the core being the most popular cards. That is to say, the deck is super flexible in terms of "needs" to meet the minimum requirement of the gameplan, but is typically built in a similar fashion.
"Loam Dredge" is what I'd label the current most popular iteration of more "traditional" dredge in that it actually runs mana sources. Historically, its a concept that I developed by merging the ideas of AJ's list and Sullivan's list ~4 years ago that was recently picked up by LSV, and seems to have started to gain some traction from that. I'd put other cards of dredge, like Creeping Chill and Gurmag Angler, under this umbrella since they conceptually fit the build of doing stuff with your graveyard under non-exile effects. I guess maybe more accurate / better names would be "Bloodghast" Dredge vs the other one that is maybe better named "Manaless" Dredge.