Helphelphelp!!

hey, sorry for the noob question, but ive recently bought a transmission off a member on this forum, which is supposedbly to be a H22a JDM auto gearbox.

i was just wondering if i was to replace my AUDM H22a auto gearbox for the JDM one would it be a bolt off and bolt on kind of thing ? or are they actually different sizes etc ?

because my mechanic said the transmission looks smaller and said its not the same.

so how can i tell from the transmission if its a h22a4 gearbox ?

in kind regards, Peter