Why are you looking for a box intake? On a N/A setup you'll just be killing your performance...
Trick Flow just came out with a new box intake. Summit carries it, but I'm sure you can find it somewhere else cheaper. An Eddy Victor Jr. would probably be a good intake as well.
Reichard Racing has them for Trick Flow & Holley intakes. I'm not sure if he makes them for stock lowers. They definitely don't fall into the cheapest category though. I've got one of these & the air gapped R lower for my 408.
I've got a black Downs box upper here somewhere. I think it's black anyway. I haven't seen it in quite a while. I'd have to hunt it up if you're interested. I could probably sell it if it'd work for you.
No problem. Send me your email address so I don't have to try posting them on here. If you take this intake, it'll be right at home as it came out of a triple black 94 vert
I've also got a set of untouched Trick Flow Twisted Wedge heads if you're interested. They'd be a nice step up from the E7's.