A standard sized sink for two bowls (however split) is 33". It's been standard for many many decades. A 70/30 split sink is a relatively modern invention, and only really works in that sized sink. Once you go under that, both bowls become too small to use. That's why you will see single bowl be the predominate choice for sink cabinets 30" and smaller. You should read the many glowing accolades for going single bowl. And one of the reasons it's such a successful choice is that 95% of all dishes are done in the DW now days.

Yes, I typically only wash pots and pans and a few extra items by hand when the dishwasher is full. I know many people really prefer just the one large sink. But, we have no prep sink area so it is nice to have that extra little sink just to drain things or scrape plates into--those types of things. That is why I am looking for something similar to what we have now. Maybe I'll have to resort to just reusing what I have since it is in really good shape.

Is this too large if not undermounted? Not a full divide, but does have separation. Bowl is 30 5/16". Wasn't sure if your custom size above was the inside dimension.

Here is a link that might be useful: kohler Smart Divide®

A 30" cabinet only fits a standard 25" single bowl sink. There are a few sinks that have come out recently that will work in a 30" cabinet, but they are all single bowl as well. The largest sink that you can have with a 30" cabinet is a 27" sink. You HAVE to leave room to attach the sink properly. Yes, some people crowd a too large sink in by cutting away the walls of the cabinet, and some of those don't even have problems with that. Some do, as their cabinets aren't robust enough to carve away their support and still handle a heavy sink full of heavy water for decades. And some people have damaged sinks and then find it's impossible to replace the sink if they've scooped the sides without either pulling the counter or completely destroying the sink base from the inside out and then reconstructing it.

You don't have room for what you want. Settle for what's available. It will actually work better than what you want.