Here are the top-40 singles from the summer of 1968. Note that tonight's "Mad Men" used "Words Of Love" over the end credits, last week it was "Reach Out Of The Darkness"...so if you watch Mad Men, you'll probably find next week's on this list too, provided the usage fees aren't too high.

Think about "Can't Wait Too Long", imagine what else Brian would have or could have added to "polish" the overall sonic footprint of the song, and as much as I love the tune I can't see it on this list, at least from a sonic/production standpoint.
Their biggest singles from this immediate era - Darlin and Do It Again - had not only a great sonic sheen (Darlin's horn section hook, Do It Again's killer drum intro sizzle and singalong choruses), but also had those qualities which made them sound like a hit - that undefinable quality that you can pick out within 5 seconds of listening.
Can't Wait Too Long is the musical equivalent of a "think piece", it's appeal can be found several different places yet it still takes time to develop and digest what's going on. It's a terrific album cut as it stands unfinished, what else could have been added to push it up into hit single territory?
Lack of words does not matter in summer 1968 standards - at least five on this chart are instrumentals, one of which won a Grammy and each of them now beloved classics that have been used dozens of times in various media, at least two of those are considered among the greatest pop instrumental records ever made (Classical Gas, Grazing In The Grass).
The Horse by Cliff Nobles and Co is strangely similar to Can't Wait To Long by design - it was recorded as a backing track where a lead vocal with lyrics was to have been added on top, but that didn't need to happen, it came out without a vocal, and DJ's had no problem playing an instrumental with a killer groove...so this "unfinished" vocal-less track sits at number 6 in the summer of '68, while Can't Wait Too Long sits in the vaults.
Look at this chart...the music is simply amazing and most of it timeless. Incredible.
Removing our BB's bias for a minute, is Can't Wait Too Long as strong of a radio/jukebox/45 song as those on this list that it could have been here had it been released?
It's a better single than D.W. Washburn, I'll say that much...
1. THIS GUY'S IN LOVE WITH YOU - Herb Alpert (A&M)
2. LADY WILLPOWER - Gary Puckett & The Union Gap (Columbia)
3. JUMPIN' JACK FLASH - The Rolling Stones (London)
4. STONED SOUL PICNIC - The 5th Dimension (Soul City)
5. GRAZING IN THE GRASS - Hugh Masekela (Uni)
6. THE HORSE - Cliff Nobles & Co. (Phil-L.A. Of Soul)
7. ANGEL OF THE MORNING - Merrilee Rush & The Turnabouts (Bell)
8. MacARTHUR PARK - Richard Harris (Dunhill)
9. HELLO, I LOVE YOU - The Doors (Elektra)
10. MRS. ROBINSON - Simon & Garfunkel (Columbia)
11. YUMMY YUMMY YUMMY - The Ohio Express (Buddah)
12. HURDY GURDY MAN - Donovan (Epic)
13. REACH OUT OF THE DARKNESS - Friend & Lover (Verve Forecast)
14. THE LOOK OF LOVE - Sergio Mendes & Brasil '66 (A&M)
15. TURN AROUND, LOOK AT ME - The Vogues (Reprise)
16. CLASSICAL GAS - Mason Williams (Warner Bros.-7 Arts)
17. INDIAN LAKE - The Cowsills (MGM)
18. MONY MONY - Tommy James & The Shondells (Roulette)
19. PEOPLE GOT TO BE FREE - The Rascals (Atlantic)
20. SUNSHINE OF YOUR LOVE - Cream (Atco)
21. BORN TO BE WILD - Steppenwolf (Dunhill)
22. THINK - Aretha Franklin (Atlantic)
23. HERE COMES THE JUDGE - Shorty Long (Soul)
24. DREAM A LITTLE DREAM OF ME - Mama Cass (Dunhill)
25. SKY PILOT (pt. 1) - Eric Burdon & The Animals (MGM)
26. PICTURES OF MATCHSTICK MEN - The Status Quo (Cadet Concept)
27. TIGHTEN UP - Archie Bell & The Drells (Atlantic)
28. I LOVE YOU - People (Capitol)
29. A BEAUTIFUL MORNING - The Rascals (Atlantic)
30. LIGHT MY FIRE - Jose Feliciano (RCA Victor)
31. THE GOOD, THE BAD AND THE UGLY - Hugo Montenegro (RCA Victor)
32. STAY IN MY CORNER - The Dells (Cadet)
33. SHE'S A HEARTBREAKER - Gene Pitney (Musicor)
34. AUTUMN OF MY LIFE - Bobby Goldsboro (United Artists)
35. LICKING STICK -- LICKING STICK (pt. 1) - James Brown
& The Famous Flames (King)
36. I COULD NEVER LOVE ANOTHER (After Loving You) -
The Temptations (Gordy)
37. NEVER GIVE YOU UP - Jerry Butler (Mercury)
38. D.W. WASHBURN - The Monkees (Colgems)
39. SEALED WITH A KISS - Gary Lewis & The Playboys (Liberty)
40. JOURNEY TO THE CENTER OF THE MIND - The Amboy Dukes
(Mainstream)
41. AIN'T NOTHING LIKE THE REAL THING -
Marvin Gaye & Tammi Terrell (Tamla)
42. HOW'D WE EVER GET THIS WAY - Andy Kim (Steed)
43. YOU KEEP ME HANGIN' ON - Vanilla Fudge (Atco)
44. I CAN'T STOP DANCING - Archie Bell & The Drells (Atlantic)
45. SOUL-LIMBO - Booker T. & The MG's (Stax)
46. HALFWAY TO PARADISE - Bobby Vinton (Epic)
47. MASTER JACK - Four Jacks And A Jill (RCA Victor)
48. A MAN WITHOUT LOVE (Quando M'Innamora) -
Engelbert Humperdinck (Parrot)
49. DON'T TAKE IT SO HARD - Paul Revere & The Raiders (Columbia)
50. LOVE MAKES A WOMAN - Barbara Acklin (Brunswick)