I've had moderate success shooting Portra 800 indoors in nasty lighting. You could always rate it at 2000 and ask for a 2 stop push. I've heard it takes that well, but I've never done it nor seen an example. In my experience, it handles tungsten lighting pretty well, as well as Fuji film. It does show the greens from fluorescents more than Fuji. You'll probably be better off correcting tungsten lighting if you underrate it a bit, like at 640 or 500.
Of course, if you can pull of Portra 400, I think you'll be a lot happier.
Oh, and send your film to a good lab for proper development (including pushing) and scans. Richard Photo is one often tossed around. I've been happy with NCPS and am trying out Precision Camera now - they have a special for RFF members.