I saw a video of Ernest Rowe doing a caliber change with the .35 barrel kit and it looked like it came with everything that a " Fx Impact Slug Probe Power Kit" but instead of a probe like in the kit, it was a .35 pelllet prob along with a heavier hammer.
I currently have the fx impact mk2 .35 and realized it's way to expensive to be plinking the way I do..
So I purchased the .22 cal barrel kit and was trying to achieve 34gr @ 1000fps like Matt Dubber lol . I purchased the fx impact slug probe power kit and was watching a tutorial on how to install it and noticed it was the same stuff that was already on the .35. Then i checked the front valve to see if they where both the same and they were.
Here are the videos i was talking about. Hope this kind of helps.
how to install fx impact 357 barrel kit :
https://www.youtube.com/watch?v=Exx3HSidRXU
how to install fx impact slug power kit:
https://www.youtube.com/watch?v=XqB3u4fW2Y0&t=261s