I was done with this string after giving my earlier advice on gear but since you guys brought up the converter possibility this is what the numbers tell me. You have 33.5 tires if that is correct then the roll out is 105.24", next you have 4.33 gear ratio. You said that you are running 125 MPH at the stripe and guessed your rpm at 6200. If your converter had little slip like mine does at 4.75% or less, then the rpm WILL BE 5701 with these variables given at 125 MPH unless there is a denominator that is incorrect in the question. If you saw 6200 rpm that would be a bad sign for the converter for sure, not an opinion. If your stator was bad and I have had one bad right from new, which made the diagnosis challenging to say the least, My car drove off the starting line like a turtle then acted like it hit the bottle 50' out. This is sort of what you were describing at first. But the 6200 rpm does not wash no matter what, and by a lot. A 31 inch tall tire with a roll out of 100" will only net you 6000 RPM at 125 mph with a good converter slip ratio so I am saying that you know what tires you have, but the converter has to be south in a big way to give the high rpm you report at the stripe based on the MPH . I gave my gear ratio advice on my guess of 135 mph based on the info you were giving at that time exempting your MPH. It's NOT tight, its just about falling apart LOOSE ! and probably with a bad stator to boot.
I would mull it over a bit before the gear change..........
Bruce