I think you have got 2 different 3racing chassis mixed up.
the whole point of the mchassis conversion is to shrink it down to m-chassis mini size. shorter & narrower.
If you dont want it to shrink get something else , like the 'normal' 3racing TT01 carbon kit.
I think thats the one youre really after
still a waste of money either way (& I have one), but a fun build.
Also expect to spend even more on 'upgrades' not included in the kits.
my m-chassis conversion