torque converter question

It's a half ton truck with prairie gears and a slant 6. A converter isn't going to make a world of difference. A gear change, a supercharger kit or another engine would be more effective.
Well it's getting another engine. Though this other engine is also a slant 6. But a slightly improved version.
Like I'd said I wouldn't even be thinking about doing anything with the existing one if I didn't think that the ring gear had an issue.if I thought that I could replace the ring gear without replacing the converter I would. But if there were any improvement to be had while going down that road, I figured now would be the time to kill that bird with the same stone, so to speak.

How would this one that I am looking at, compare to the original stock one? (Assuming again that what is in there now is a non lockup version) I'll have to either wait till I have it apart to see, or get that PK number from it and see what I can decipher from that.
If I find out that it is a lockup then I'll be looking into a "rebuilder's special". It drives like the one in it now, is a non lockup.
And I have never heard the term "prairie gears"
What is meant by that?
Can anyone answer me on whether the converter I am considering is a 11 or a 12" unit?