Hi Will
I very strongly believe that you should not discuss your transition at all. I know how much we want to be true and open, but it's really very possible that the engineers will just not want to have a "freak" amongst them. That's how they might see it. And let's be honest, they have nothing to lose at this time by not offering you a job.
You need to negotiate from a position of maximum strength, reducing all doubts to an absolute minimum, and emphasising how appropriate you are for the role.
Transitioning is not a terribly rapid process, so you can start transitioning on the job, and if your company is anything like mine, they won't notice a thing for quite some time, probably closer to a year (unless you do something radical like FFS!) That time will allow you to become part of the team, to demonstrate your ability, to become a trusted colleague. You don't necessarily need to be a "real man", just a genuine colleague. And once you have become an integral part of the team, it's much more likely that your job will be secure when you announce your intentions.
You might want to have a look at a thread I started here about 2 months ago. It's not entirely aligned with your situation, but it is an engineering company:
https://www.susans.org/forums/index.php/topic,159687.0.html I'm really happy to discuss this further with you, look at scenarios, risks etc.
Hugs
Julia