How do I know what size of long dresses would fit my size?

It's always difficult for a man to get the right dress size--usually because he is obliged to rely on "plus" sizes to get something that fits. Believe me, i know! What kind of alterations do you think you'll have--breast implants?

We have a tall drag queen in town, she’s 6’5 and that’s without the heels, I’ll text her later and ask her where she buys her clothes and get back to you later.

This is the best formula:
Your age (your mother's current weight/grandmother's bra size) = your dress size
Your shoe size (Pi)^3

That's a good idea. I'd also suggest talking to female friends, find out which companies have accurate size charts as many of them don't, and then take your measurements. You might want to have someone else do that, at least to start, and then check charts. I would suggest, also, that you size up if your measurements seem to fall between sizes. Men's arms can end up being wider, too, so close-fitting sleeves might not fit so well, as the arm holes might be too small.

Or......

Add the height of your father to that of your mother and divide by two, then add twelve inches.

If it's a business dress, take off four inches and divide by the length of your shoe heels.
For a dinner dress, add twelve inches to the original formula and wear a good quality pair of spanx.

Stephanie is so big she has her dresses made.

And her shoes, too, I bet. I love her jewelry.