you're forcing oil through the cooler core so the alignment of the cooler shouldn't impact that. There may be some cooler designs that this would not apply to, but the Setrab 6 series coolers are what I used in the race cars and I've seen them mounted in all configurations without issue.
Z1 Motorsports 770-838-7777 ex 302 www.300zx.com AIM bryanatZ1