Sorry for the Necroreply: But I'm upgrading the FT Prusa i3 2020 to the p3steel v4
AFAIK, it depends on WHAT upgrades we are talking about:
The biggest changes I've seen so far are:
an increase length and diameter of the y-axis smooth rods. (10mm x 510mm)
But perhaps his Github wasn't as refined a year and a half ago. https://github.com/AlvaroRey/P3Steel_V4_20x30
But, as is the custom, I'm sure I'll be doing a little bit of trial and error when it's time to swap frames.