I've heard the contrary about fitment.
I will absolutely not try to put the two together until I have an approved form 4. I can report back in 7-9 months =P
They fit.
It will be a form 1 you use to build an SBR.
If you use a trust and file and eform, it could take as little as 3 months. If you use a paper form, it could take as long as 15 months.