For something like your doing, I'd probably plant them 2 feet apart. Get the rows on out there to 30", maybe 3'. Not familiar with any heirloom varieties. I've got a sneaking suspicion, that the plant will be shorter than what I'm used to seeing, with smaller and narrower leaves. Might be giant, but I doubt it.
I wish I had a nickel, for every hour I've spent in a tobacco patch. It's honest work, that makes men out of boys. You hold that dollar a little closer, when you earned it in the tobacco patch. I can't even believe how many fond memories, I have of my time working in it.
Sadly, I remember the day I started using cuss words. Wish I had that day back. I was pulling gympsum weeds up, and carrying them to the end of the row and throwing them in a hog pen. It was dark tobacco, that is far more brittle than burley. I had to carry them out above my head. Nobody around for miles, just me, a jug of water, and a few packs of crackers (my dads prefered way to leave us in the field. If he never picked you up for lunch, you had little to complain about). I decided to give cussing a try. I cussed the tobacco, cussed the heat, cussed the hogs, cussed everything in sight. No doubt in my mind, those hot days molded most of the decisions I made later in life. Wish I had that sad day back.