$120 fron nissan for a rb20 one.
unbolt your oil cooler/filter housing and bolt the 20 one in its place. use a z418 filter, not the genuine nissan 145 as you no longer have a relief valve.
(rb20 has it on the block, where as rb25/26 has that part blocked off and instead has them in the oil cooler/filter housing)
if you are using a remote filter, put the oil pressure sensor in it there, and lengthen the wiring to it. if not then use the 1/8 npt port to the rear of where the filter/cooler housing bolts on to the engine. (at about cylinder 5 along the block)
nismo has a replacement housing, but its like $1000. it has 2 -12an fittings where the cooler sits.
also nismo has a oil cooler kit, said housing, with a custom aircon condensor with a 25 row oil cooler integrated into it. i have one in my garage. i had the brocher for it but i lost it. was an option for the aussie deliverd ones.