ga,
The 76B would be a good aircraft for your job. P&Ws better than Arriels for that sort of work. Only problem is 76 needs more maintenance than the 365. If you're looking at 365 the only one for that would be the N3 - a good hot and high helicopter needing less maintenance and burning less fuel than the 76B. I like both machines, but depends on what you want to do with them at destination. The N3 cabin is a bit smaller, but with the sliding rear doors and ease of removing seats to transport freight or stretchers I think it would be more versatile. The 76B with the PWs has EAPS already to deal with the dust, but you might need to think of fitting sand filters to the N3.