Go somewhere else. The factory did it with a "Y pipe from the pass to the driver side and then under the trans mount back to the axle and out the rear valance. Whats the problem? Are your 273 manifolds the real ones that point straight back, or do they point down and a little forward? If you want to run true duals, you can get a later year trans cross-member that has the dual cutout or cut your own.
