As far as i know the early ones had a shorter stroke 82mm i believe.
The newer ones are longer stroked at 96mm I believe.
Other than two extra side stock screws,on the later ones.
And different springs.

Did the seal easy peasy How did you get on with the short stroke? Hi. I took the short stroke off after about 20 shoots. The power dropped down to 9.5 ish and I didnt find the hold sensativity was any better plus the cocking stroke was a lot harder. I dont know if it was because it was a TX HC but ...

I short stroked my tx 22 it's worked out very well but I don't think I would try the same with my 177 pro sport because of the power loss , you would have to shim the spring up to much to get the power back, which would make it harsher again which would defeat the object . Regarding your coments on...