I saw the other post you mentioned but it only had a couple replies when I lost track of it. I didn't reply to it and I'm hesitant to reply to this so keep in mind this is just my opinion. I'm not telling you you shouldn't or can't run a 3 speed. Some folks do and do okay with it but lot's of others ask the same question you are for the same reason.
In my opinion, you have to much low gear. It seems like you're onto that by wanting to change the rear gear. You might want to look at your starting line ratio. Here's a couple for your combo:
4.30 gear/2.45 low= 10.54 SLR
3.90 gear/2.45 low= 9.56 SLR
Now here's a couple for a commonly used transmission with a stock low gear:
4.30 gear/1.76 low = 7.57 SLR
3.90 gear/1.76 low = 6.86 SLR
You can see that the low (trans) gear ratio makes a bigger change than the rear gear change. You'd have to drop to a 3.20 gear to get close to the same SLR as the 4.30/1.76 combo which would have you crossing the finish line at a lower RPM than I'm assuming you'd like. Essentially numbing up your car and taking away performance that I'm sure you'd like to see on the scoreboard.
So what does all this SLR stuff mean? A lower SLR is good for lighter cars even with moderate power. A higher SLR is needed to get heavier cars off the line. But then again a heavy car with a ton of power generally needs a lower SLR.
I would never tell anybody what to do but this is my opinion and it's backed up with real information. Don't take it from me as fact, research it yourself and draw your own conclusions.
