Yes (like I said) you can on a P/U.
The pipes go (side by side) all the way past the rear axle & then turn 90 degress with small mufflers with tips that exit on the passenger side.
Patrick's has the perfect muffler (2 in 2 out)for that. But that's inline stuff.
For your 500 CID Caddy, same answer. Run the pipes the same with each turning L/R just past the rear end. Now put the smallest glasspack that will fit (clamped) there, then a short tip outside the bed. The "tip" need be only a few inches long.
If It's to noisy, switch the glasspacks for Cadillac resonaters, which is what GM/Cadillac had, minus crossover & mufflers.
JM...
