I also like "The Locomotion", and "Shinin' On" from that period.

Their Ultimate Hard Rock song for me was "Inside Looking Out".

And I just love the bass line opening to "Black Licorice". Which is followed up very nicely with "The Railroad" on their 1975 live album CAUGHT IN THE ACT.

Mark, Don & Mel 1969-1971, and Caught In The Act are my go to albums for Grand Funk material.