I have one,,and it's placed on the left side of the bus in between the outriggers. an extra 1,5 liter wont hurt in any way
My oil cooler got a fan on it. When fully packed bus going up long hills, oil temp can get to the upper limits, i then turn on the fan, and temps go down 6-10 degrees C.
I was going to suggest that you might required a extra cooler with the bigger motor!! Some road miles will answer that question
And if you have a full set of belly panels and the bus is a bit lowered where is left to put a cooler ? Reason is I realise I messed up planning the summer trip and need to take an 850 km blast down France in a day in July. The engine survived at oil temp 120 and 110km/h during a similar mad one day run home from Cologne stopping for petrol and a break three times but it was in a cold April.
I've got an external oil cooler and a thermostatic take off from the spin on filter, ive located the oil cooler in the spare room at the moment though, and from there it doesn't seem to cool the oil too well