Swapping out the heater core on my 110. Factory it was 2.5 NAD but now has defender 200TDI. The heater core I removed has the 90deg inlet and outlet pipes which face downward. Most heater cores available here in the States are straight pipes for inlet and outlet although the 90deg pipe ones are available in U.K. Is there any reason I cannot or should not use the straight pipe core? Thanks