First off. Welcome from New Mexico.
When you say "box pleat" what do you mean? Are you referring to the Matt Newsome 4-yd box pleat. Or, are you referring to the 8 yard military box pleats? Also, your tartan in 16 oz. will certainly not have to be special ordered. If it were me, I would go with the Strome range from Lochcarron. The Grant Hunting tartan is the same thing as "Black Watch" tartan. And, Lochcarron carries it in three shades (modern, ancient, and weathered) in their 16 oz. Strome weight. What other items do you need? Prince Charlie? Argyle? Ghillies? There are several people here that can help you with any of those things.