you could face them towards each other and wire one out of phase so that one sub fires out as one goes in. dont know how thats gonna affect sound though
This is a simple push-pull configuration, and you will still have the same space issues, and lose 3dbs.
if you do isobarik loading, you'd only need 1/2 the volume for one woofer then for both. This might actually help u get them both in your truck, or get smoother roll-off if you've got ur box built already. But you'd still lose 3dbs