I also have a 231/237 TSP cam. I've dyno'd a few times (though due to overly sensitive knock sensors, I had really poor HP numbers), and I get peak HP at ~6550 rpms. I think it's a great cam for a M6, but even with a SSF3500, your shift extension is about 4500 rpms. You'd want something with a lot more shift extension (more like 5800-6000) to really optimize with this cam. So you'd want more like a 4400 stall converter. If you're limited on funds, you might want to consider a cam that peaks a little lower in rpms.
Just my two cents

I did not mill the heads. I am running stock GM gaskets. I did not have to fly cut at all. The clearance is fine.

I have the TSP231 cam w/LS6 intake, LG Pro long tubes, Vararam, and home mildly ported LS1 heads and I made 421/385 with my previous BETTER heads and I make more mph now with these heads untuned so I would say 430/390 ish the way it sits untuned.