I haven't done a full conversion yet.
To convert the .1 to a .2 you will need
13mm shocks with the 13mm springs
Diff cases (which the .2 ones have the bulkhead molded on, its not like the .1 with aluminum brackets and such)
Battery strap and mount
Gullwing shock tower and arms
Chassis
Ball cups
And I think thats the majority that is different, I might be missing something.
With my .1, I tried to install the .2 battery strap, note that it only works with the .2 chassis, unless you mod the .1 chassis for a new hole for the screw.
I have the .2 gullwing arms and tower, haven't installed them yet, but will compare it to the kit included ones (performance wise?)
IMHO, its not worth converting a .1 to a .2 if your just doing fun local club racing. (Like me), You could possibly upgrade to the .2 parts when you break a kit part. Or if your doing it like on the competitive side, yes upgrading to the .2 parts might be better for you?
Right now, I'm just sticking with kit parts, or OEM replacements. But once I get more into the competitive side of things in the future, I might.
For reference, you don't need a new and updated car to run it, my uncle runs a XB4 from 2017, and still does pretty good against my .1, and other locals that have the .1 also, 22X4, B74.2, and other brands like Tekno, Xray, Schumacher, Yokomo, ect. (Xray setups from the kit, are pretty good) The owner of the track has a XB4 2013 I believe? And he still runs it from time to time. Note, that car takes 2 1s Saddle packs, not a ordinary 2s Shorty.