I have a trust. I added a stripped lower to the trust, then completed a form 1. 90 days later my stamp came in the mail.
You could form 5 it through the department. It would then be owned by the department. There is no tax liability on a form 5. A department can transfer a form 5 weapon to an officer tax free if they decide to at a later date.
Or you can buy a sbr on a form 4 as a trust or individual purchase.
I just started the build but I didn't mount the barrel into the receiver until my tax stamp arrived. I advise you to go for it. It's a fun toy that comes out every now and then.