I just popped a Seth neck into my SG, and I think it does the Creem thing rather well. I'd bet a Jazz would work pretty well, but for your type of music and your type of instrument, I'd lean towards a Seth Lover or a Pearly Gates.
Exactly. For Clapton Cream and Bluesbreaker tones, the 59's are perfect in an SG.
However, when I saw Clapton play that SG live in '67 or '68 his soloing tone (bridge pickup mostly) was to die for and his chordal (neck pickup tone) was muddy.
Both pickups in his SG were identical and probably wound to around 8K.
The Duncan 59 set is wound to about 7.4K (N) and 8.2K (B). So the neck pickup in a 59 set would be a little clearer and have less bass than what Clapton used and, IMO, would be an improvement over what Clapton used.
The Jazz N might be better still...a little less bass, more upper harmonics and clearer but still ballsy tone.
Lew's right. The '59 is a good choice. The other option is the Seth like MattPete said. I've had a pair of Seth's in my '61 SG reissue and nail the Cream-era Clapton tone pretty well. The '59 will be slightly brighter, but within the same ballpark.