have you checked the oil pump for clearance as the courier will require the bulk of the sump to be at the back
a friend of mine fitted a 253 to a courier around 8 years ago & has since replaced it with a 308 & has done heaps of interstate trips in it
he initially ran a small radiator & increased its capacity by running water through the alloy bull bar, we always got a laugh when he pulled up for a chat & somebody would lean on the bull bar & then
it now has a custom radiator fitted & it all looks factory as its all including the engine painted the deep maroon color the same as the body
regards
rod