No idea if anyone would be interested in this but, I recently started this 1e version of Rappan Athuk with my table group and after reading it I wanted to **spoilers** do a more direct by-the-level approach versus PCs haphazardly stumbling into a room with a CR way above there ability. (I know this is kind of the point in a way to give it more of a dangerous feel, but I wanted a full 1-20th level campaign).
So below is a pathway to this. The entry and exits have to be adjusted but since the PCs don't know where things go, its been easy to railroad them from one map to the next appropriate level map.
Start
PCs level page
1-2nd 130pg
1-3rd 151pg
3rd 95pg
3rd 107pg
3-5th 193pg
4th 150pg
4-6th 122pg
5th 210pg
6th 139pg
6-7th 218pg
7th 241pg
7th 460pg
8th 62pg
8th 73pg
8th 159pg
8th 245pg
9th 56pg
9th 228pg
9th 236pg
9th 279pg
9th 406pg
9th 477pg
9 (16) 168pg
10th 114pg
10th 202pg
10th 257pg
10th 273pg
10th 286pg
10th 322pg
10th 336pg
10th 454pg
11th 483pg
12th 264pg
12th 304pg
12th 311pg
12th 329pg
12th 365pg
12th 372pg
12th 389pg
12th 396pg
12th 432pg
12th 471pg
13th 418pg
15th 412pg
15th 467pg
15th 467pg
15th 496pg
15th 503pg
17th 512pg
18+ 523pg
20th 179pg
20+ 543pg
For my campaign I set the entrance of the Mouth of Doom under a ruined castle on Devil's Elbow just off the coast of Riddleport with the mouth's access tunnel doubling back towards the city for additional hidden entrances.
I know its a bit late, but hope it helps if anyone is running this 1e, 2e, or whatever.
:)