This next feature is a bit of a mystery to me, mostly because I profess little acumen when it comes to identifying 50's Plymouth products, and can't tell the difference between a Plaza, Savoy, and Belvedere without consulting my handy Spotters Guide To 50s Mopar, but what I can tell you about is custom El Camino'd '56 Plymouths. Those, I can spot. Here is one. Find this 1956 Plymouth Suburban (Wagon) converted to El Camino offered for $13,900 in Los Angeles, CA via craigslist.
From what I can glean from a brief look at the Allpar.com article on the '56 Plymouths, this thing started life as a Sport Suburban 2-door model, which was a pretty basic thing, with rubber mats instead of carpet in the cargo area.
Power comes from a 277 cubic inch Hy-Fire V8 that puts out 187 horsepower and 256 ft-lbs of torque. There was an optional "power pack" that added a 4 barrel carburetor and dual exhaust for those who wanted a little more oomph.
This features a surprisingly well done bed area, complete with functioning tailgate and a few coats of some kind of bedliner. With any custom car, the devil is in the details, and this one might just have what it takes.