Best place for ground under dash?

i recently re-wired my entire car. i got a power and ground junction box. you can see them in the picture. they allow you to attach multiple wires and then get a good power/ground source. my ground block was run to a very good chassis ground with 6 a wire.

I have a junction block on the other side of the firewall for the B+ stuff, just need a ground place to tie in multiple things.