Chess definitely had a fairly stable rhythm section pool of players who they used during the Billy Davis era (62 to 68), their horn sections however were more a case of whoever, there was little stability there. As far as I've been able to establish it is very hard to confirm exactly who plays on what, I can't find any written reference to the funk bros playing on any particular Chess 45s, but with the Billy Davis connection it's not impossible as they are known for sure to have played other Chicago sessions for Brunswick etc. Also they had a lot of stuff on Chess through their St Louis (Oliver Sain etc) & DC (Billy Stewart, Knight Bros) etc connections which were recorded out of town, not to mention the Muscle Shoals stuff too. With Tony Clarke's Detroit connection he may well have used funk bros, Valentinos may just be their road band, who knows for sure?