I do not think there are exact measurements of the process, at least from what I researched.
I had mine cut off the tunnel like yours so what I did was lay it on top of the pan in my car and fasten it down. You have the hole and the rear seem so it should be easy to line up. After that, I took my cut off wheel and cut through the welds of the brackets through metal and nicked the floor pan on my car so I have the spot where it should be welded. This should keep it straight.
Once I finished that, I very lightly tack welded them in place (in case I was off and I was) and fitted the linkage and slap shifter. On a side note, make sure your transmission tail housing has the two bolt holes so you can attach your linkage to it(ask me how I found out). I put the console over it and it bolted right up but something I forgot to do was check it for being level. I was straight on the brackets but the middle one angled down to far and it listed to the left so make sure its level across too. It was only tack welded so it was an easy fix but glad I did that as a precaution.
I am sure there is a more professional way to do it but that is how I muddled through it. hahaha