In 1955 we ran a303 Olds. in a 49 chevy coupe. It had a Weiand intake with 3 stromburg 97's, an Ed Winfield cam, (boy could he grind camshafts), stock valve springs in cleaned up heads milled to 9 to 1 compression. Homemade headers, dual point ignition and everything else stock. It pushed the coupe to 140 mph at Bonneville. It was hooked to a Packard 3-speed tranny via an adaptor. Somewhere out there should still be equipment for that engine.
Regarding straight pipes, it's trial and error. Long pipes are good for low end torque and decreasing in length for better scavaging at the upper end. For a rat rod though, looks play the part.