The only transcriptions I could find of this song were the orig. Marvin Gaye/Tammi 
Terrell version, 
so I came up with this. (as you likely know, the Diana Ross version is a complete re-working,
almost a different song, altogether) 
I worked this out on the piano, so I don't know how that translates to guitar. 
It is not presented as a note-perfect dictation of the record, but rather as 
attempt at a faithful, 
yet playable version. Some of the chords, I know are dead wrong. 
I've taken the ball as far as I could run with it. 
Hopefully, I can incorporate any changes or suggestions y'all might offer. Cheers.

Ain't No Mountain High Enough (Ashford/Simpson) -Diana Ross version

Intro: single notes over a B bass note
       (F#-B-F#-A-B-F#-B-A-B-F#-A-B-F#)/B     Cm/Bb Cm/Bb    C/G

Cm/G | Bb/F Gm | Cm/G | Bb/F C or C/Bb| Cm/G |Cm/Bb |Bb 
        Ahhh ahhhh ahhhhhh   ahhhhh   ahhhhhh  ahhhhhh  ahhhhhhh

Cm/G         Bb/F (102220@1)    Bb/D (x1033x@1)                                   C/EIf (x3111x@5)you need me, call me. No matter where you are, no matter how far
Cm/G              Bb/F (102220@1)    
Just call my name.    I'll be there in a hurry
Bb/D (x1033x@1)                   C/E (x3111x@5)On that you can depend and never worry

(same chords)
No wind, (no wind) no rain, (no rain) Nor winter's cold
Can stop me, babe (oh, babe) baby (baby) If you're my goal
No wind, no rain, Can stop me, babe, If you're my goal
                                             
  Cm/G#                            Cm/A     
I know, I know you must follow the sun, wherever it leads
                   Gm/Bb                         Gm/B  
But remember, if you should fall short of your desires
                    G (320003@1)  C (x32010@1)              Bb (x1333x@1)      Cm/D#       Cm/G# 
Remember life holds for you one guarantee,   You'll always have me

Cm/G#                                               
And if you should miss my lovin' one of these old days
Cm/A                                                      
If you should ever miss the arms that used to hold you so close
       Gm/Bb                            Cm/B            
or the lips that used to touch yours so tenderly
Cm/G  Cm (x3101x@1)                 Cm/D#         Cm/D#  Cm/G#  Cm/F  Cm/D#  C (x32010@1)     Just remember what I told you, the day    I      set   you    free

(staccato)
Cm (x3101x@1)                             Bb (x1333x@1)            GmAin't (355333@1)no mountain high enough,   Ain't no valley low enough (say it again)
Cm (x3101x@1)                          Bb (x1333x@1)         C (x32010@1)  
Ain't no river wide enough to keep me from you  2x

B/F#   C# F  B/F#  Bbsus2/D#

Cm/G              Bb/F (102220@1) GmAin't (355333@1)no mountain high enough
Cm/G            Bb/F (102220@1) GmAin't (355333@1)no valley low enough
Cm/G                 Bb/F (102220@1)       CNothing (x32010@1)can keep me, keep me from you