What guitar is it going in? Without knowing that i can't really help you.
i'd strongly advise you against the invader for a seven. It's way too muddy for most rigs and guitars. the exception would be a maple bodied guitar or you have a really bright and tight amp.
The Inavader 7 might work but imo it's still too muddy for the low b. if i were you i'd go with a Custom-7. It's got balls tightness and clarity.
For the neck there aren't as many options as for the bridge, but i think the Jazz-7 should be your best bet if you want to SD exclusively.
If not have a look at the Dimarzio Air Norton which makes one of the most popular and imo best 7-string neck pups
I appreciate the helpful input and feedback. I've got a few things to consider now. I am partial to the SD's, having had very good experiences with them in previous guitars.