Wow, thanks for all the responses! here's some pics from this evening. Mostly just cleaning up the fillets on all the seams today and filling some of the 500ish screw holes. I'm going to seal the inside with black epoxy so I'll have a nice dark background. The outside will get filled and sanded then finished with a light grey or white gelcoat.
It will have a 50gal sump and bio tower underneath with a couple of pond pumps running it. Haven't made a lighting or substrate choice yet. I'd like to go cost effective on the substrate - so I was thinking like 3/8" gravel from a concrete yard or something, but I'd also like to go dark. black slag looks very nice, but I've read it has a lot of health consequences for the fish. Anyone have any dark, cheap substrate suggestions?