What is the income level of the tribe? Just serving native groups is not enough to qualify. I do an awful lot of 8A work, but don't take credit for all of it. You need to justify the need for the income and the revenue stream back to the tribe. (IE the corp will funnel the profits back in the form of infrastructure improvements, dividend payments, whatever).
You can easily use the "broader statewide" line
if you can show the need (LMI value). I do it all the time. But, you have to also be meeting the needs within your AA to get that credit, so be sure those ducks are in a row.
On the credit side, do they have their 8A yet? They're getting harder to get now a days, so we like to see the certification first, before going too far down the credit structure line.