To answer your first question; Yes Mercury built pickup trucks. They were only available in Canada from the mid-forties all the way through the mid-seventies. They are basically re-badged Ford F100s with some trim changes, but they are quite rare and unique.
Even rarer is the fact that Ford/Mercury made "Unibody" trucks for the 61-63 model years. The trucks had the cab and pickup bed as one piece, which is how they got the Unibody name. The problem was that stress cracks developed from loading the pickup bed with too much weight and the cab couldn't handle the stress. Ford cancelled the Unibody after a short 3-year run.
Now to make things triple-rare, this truck is a short bed Mercury Unibody with a Big Back Window (or BBW). The BBW was a special option on custom cabs that provided a large wrap-around rear window with nice aluminum trim. Its a pretty rare option and I've only seen one other short-bed M100 with it. As a matter of fact, it's the dark green truck in the gallery below.
My truck is a combination of Mercury, Ford, and aftermarket stuff. Most of the body is from a Merc, but I grafted on a roof with a Big Back Window from an F100. I also had to repair some rust in the floors and fabricated a new firewall and pickup bed floor. Everything came out pretty good and the truck is almost ready for final prep & paint.
FYI - there are several pics of my truck below, which was originally red, but after I finished the metal fabrication I sprayed it in SPI black epoxy. There are also some rendering of my truck as I plan to finish it - those are the green body with red wheels. In the gallery, I have also included pics of other Ford and Mercury Unibody trucks that have inspired me.
It's number 1 on my priority list.
Ford 454 FE with about 550 hp and 600 ft lbs torque.
Centerforce clutch, Lakewood Bellhousing, Tilton TB, and a Richmond 6-speed.
Custom frame built by me with Mustang II IFS and a triangulated 4-link rear. Air Ride Technology Shockwaves all around. Baer 13 inch disc brakes all around.
BODY & PAINT
Lots of sheet metal fabrication and repair with a new roof. Its a work in progress, but planning a dark Olive Green metallic with Candy Apple Red accents.
Haven't even started.
WHEELS & TIRES
Coddington 22x12 in rear with 305/40-22 BFGs. 20x9 in front with 265/35-20 BFGs.
I am finishing up a new IFS that gives me some more clearance and then I can start the final build process of completing the frame and getting the drivetrain installed.
I've already finished all the major sheet metal fab and repair and have it ready for final body work and paint.
Theoretically its only a few months of effort, but based on my work load, it could take me until the end of the year.
So many ideas, so little time....