Damn, that's gonna be a fun build! lol My max dimensions I came up with were 37 wide, 16.5 tall, and 20 deep. She fit REAL snug for me. (When trying to go in from the trunk) Ended up being 4 cubes after all displacement. I will just say GOOD LUCK!
You'll figure it out. Worst case, try to get as much space as possible, then just compensate with more power down the road. You got the dual-1 option so you could throw a couple mono-blocks on each channel.
We'll see how she does on the 2k+ first. An aero port would help save you some internal volume as well. Here's my 4ft^3 box in snug:
