The only Hilux 18R sump I've seen had a pretty similar mid-type layout as the 18RG/RA28 set up.
The only difference I could see (without direct comparison) was that the Hilux sump had a large drop-down extra reserviour section at the back of it. The plug was in this part.
This extra reserviour would be pretty important as the hilux would be expected to deal with different running angles that an RA28 would normally, what with 4WD trails and that.