I had a '92 S-10 with 2 MTX Blue Thunders in separate Truck boxes the ones they used from factory with the port built in. I had so much room behind my seat even with those I still had full leg room. But times have changed since then for the amount of room they give you I think in a single cab. Damn I miss that little S-10 2WD with the Vortec 4.3 man could that thing scoot especially with the headers, exhaust, cam upgrade and intake/injector upgrades,lol.
Idk best bet is to take pictures, measure it all out exactly and send it all to buck and see what magic he can do with it.