In general : To imitate a photograhers special look is absolute allowed! Later you may find your own look - ALL photograpers did it!
You perhaps should find out wich films Moriyama used! It was within the 70s!
If you have no information you better use a film from that period Moriyama did use bw film!
So don't come up with D3200! I would begin with HP5 (good push performance)!
Do you know how to underexposure (many do but are not knowing....
) it is real easy :
Regarding your correct messurment you may use a stop 5 - 6 times below (5 stops slower)!
This pic above looks like !
Next is to push the film up to a point grain is massive! Some who came along next would advice you to use Rodinal (they identify grain and decide : best for Rodinal) that may be OK - but is it all time such easy? (grainy look -> Rodinal) ?
Be sure Moriyama was not such an easy guy! I would start with total normal developer!
with regards
PS : If you compensate underdexposure via pushing HP5 you would get enough grain form my point!
What I perhaps would start with is Xtol
! Look at the sharpness of that you would like to imitate!
Hp5 is "relative neutral" from sharpness (there are better films for high resolution out there)
But Xtol would indeed outperform a sharp grain! An other hint is Neofin blue!
But it is on you - you can use each normal developer - but pls. NO RODINAL
!