Motowniest Motown Song?

[Boogiedown]

I'd say:

I Can't Help Myself - Four Tops
You Can't Hurry Love - The Supremes
Dancing In The Street - Martha & The Vandellas

In many ways I think that the driving drum beat + tambourine + guitar pluck + solid bass line = The Motown Sound

I'll go with those three choices as well , they each have that classic Motown "vibe" you're describing.