Which Qctp?

Howdy folks, me again, the clueless noob. I have been lurking around and noticed many folks with lathes similar to my QC-54 have a quick change tool post. I looked aorund online and there are many out there but none come right out and say, "this will fit a QC-54."

So can anyone tell a guy who will need specific instruction for even the simplest task just exactly what size will fit my machine? Maybe the best place to get one for not too much money?

I know, I am cheap, but I have good...

Which Qctp?