Well, it could be worse: you could be trying to mix lead-acid with NiCad.
You've obviously seen by now that the SLA's cannot be "equalized", while the flooded batteries need it if they're to last a long time.
I started writing assuming that you have some of both types, and trying to splice them together. Now I realize that maybe you only have the sealed batteries. Is that right? If so, you're probably okay, you even have a spare (no matter how you connect them).
The C40 will have no trouble managing the charge of the batteries. There's a jumper in there to set for AGM's, preventing it from equalizing them.
If you were to mix flooded and sealed, you'd have problems. If this was "salvaged" stuff, then I'd say go ahead and put them together in separate strings, and set the C40 to manage them like "AGM" batteries. Every couple of months or so, or whenever the wind is strong, disconnect the SLA's, disconnect the C40, and let the wind over-charge the flooded string of batteries for a while. That's kind of managing the batteries manually, but at least you don't have to do it too often. Not the best but if everything was free, then there's really no cost if you screw up.
I doubt an Ametek and one solar panel could equalize many golf cart batteries, unless it was really windy and sunny at the same time...