greddy and koyo have the same thickness (pretty much)
When using either or, u reverse the brackets so it sits lower. GIves enough clearance for SMIC

I wouldnt buy a used radiator unless i was desperate.
Even with light use, You never know whats actually going in the radiator. what coolant was used etc
it could very well be clogged or had any other type of build up that you cant see.

try to avoid JAPSPEED or those type of junk. Their fitment SUCKS ***

i have used koyo, fluidyine and greddy... i have been happy with all three of them with no major fitment issues