mufflers

I have a 78 El Camino and I want to put duals on but don't want to loose my ground clearance.
Is there a muffler, possible out of a Camaro, that has 2 inlets and 2 outlets?
The EC is all stock at this point, 305 2bbl with auto and 2.73 rear, but the exhaust is about to fall off. The plan is to keep the stock manifolds and install an X pipe with the new muffler in the stock location behind the axle.
Also, who makes body bushings for these things? Just looking for stock rubber ones. Thanks