has a large library of adapter plate templates, and chances are they have a template for a nissan pickup already, but they are known to be slow to respond and slow to get work done, but they are legit and among the "senior" EV conversion and parts companies. If you've got the book "convert it" by mike brown, that's the guy behind electroauto.
Also any decent machine shop can do the work, but if it isn't something they do a lot, it will probably be more expensive.
As for clutch vs. clutchless, its a holy war but for a first time conversion IMHO keep the clutch. It makes shifting easier and provides another failsafe motor disconnect in the unlikely event of a shorted controller and the failure of all your other failsafes. the only real downside of keeping the clutch is 20 or 30 pounds of additional rotating weight which will reduce your EV's overall efficiency slightly. You can still do things like have your flywheel lightened and remove the ring gear to improve efficiency a bit over a stock flywheel and clutch.
My car still has a flywheel and clutch, but if and when I have occasion to disconnect the motor from the tranny again, it's going clutchless.