Seen it done on a turbo'ed hilux. Was mounted at the front and in a cross flow configuration. Lots of discussion on this matter at aussie surf site
http://www.toyotasurf.asn.au/forum/sear ... de=results
If you top mount it have to work around issues with the placement of the oil filler...
I front mounted one on the lux with my daihatsu donk and was well worth it.