
I'd take that truck from my work. 400hp diesel engine, 15 speed transmission, locking rear diffs. The cab is steel, the radiator is steel, the bumper is steel, and the deck is steel. It's already a Juggernaut before I get to playing with it. I often push fully loaded semi-trucks with it, so I know it'll push your average abandoned car around. Plus it was built in 1979 so I know its easy to fix if it breaks down.
Plans? well I'd extend the cab so I can get more people in. Cover the windows with either steel decking or expanded metal from debris. Anyone ever watch Tremors? remember when they pulled that big end-dump trailer with the bulldozer to get the people to safety? thats plan A for moving people. I'd leave the wrecker deck on (winches are handy) but build up some sides on the back for storage/Firing positions. might throw a simple plow on the front if I find that I'm driving over more things than through them. thats my Juggernaut.
NOW, for my zombie killin' machine:

My pickup is a 84 Dodge crew cab, it's already got heavy duty bumpers, diffs, and tires. Because the bumpers are steel and mounted directly to the frame, I can weld a plow, spikes, blades, whatever the hell I want to them with either bolts or welds. Cover the windows with steel with gun ports, cover the windsheild with steel grating, mount two M2's on the roof on coax mounts so they can fire 180* firing arcs on each side from the roof. Have another M2 on the rear tailboard for rear coverage. build a simple light bar for a number of LED flood lights (low amp draw, long life, super bright) facing both ways plus to the side.
my truck has proven to be reliable, tough as nails, and has more than enough gear reduction to push, pull or drag anything I chain to it. plus, like the Jugg, its old so its simple to repair.