I think your time and energy would be better spent on other things then bulletproofing a vehicle personally. Maybe have some thick sheet metal to cover the windows laying around the garage just in case but welding armor or such right now would be pretty extreme.
I'm with Dean on this...
I think making an improvised APC (Armored Personnel Carrier) is a pretty silly waste of time, energy and resources!
---------------------------
If you DO decide to do something this silly,
Keep in mind that STEEL does NOT make a very good bullet defeat!
Steel works OK for shrapnel, but the directed energy of a bullet will defeat a LOT of steel in short order.
I can blow right through a 3/4" steel backing plate with nothing more than a .30-06,
And I can blow through 1.5" of steel with a .30-06 Armor Piercing round...
---------------------------
Bullets are VERY hard to defeat head on,
AND,
If you attempt to defeat them head on, you will have to absorb all the energy they carry with them, which is a BUNCH!
The best way to defeat a bullet is to 'Yaw' it.
If you Yaw a bullet in flight, it will break it's own self apart,
and you will only need something strong enough to take a glancing blow...
OR, to have the bullet hit something MUCH more prone to break the bullet up than steel...
CERAMICS are the best way to break up a bullet.
Ceramics will fracture when impacted, so a large plate isn't the best idea, smaller plates that overlap are a better way to do things...
If you don't have a bazillion dollars to make custom ceramic panels, then use ceramics little, cheaper brother,
Bricks.
You would be surprised what a common red brick will stop!
Tatictals in Somolia had bricks in the doors and bed sides, and that stopped 90% of what was thrown at them.
Many APC's from poorer countries add concrete slabs, looks kind of like bricks, to the armor to defeat AP rounds.
------------------
If you were going to 'Up Armor' or 'Hillbilly Armor' a common vehicle, I'd take a que from some of the poorer countries...
Somalia in '94 our forces were frustrated by what the locals called 'Tacticals'
That would be a light pickup with bricks stacked in the doors and bed walls, and a heavy machine gun or recoilless rifle mounted in the back.
Baltic Republics were shooting the crap out of each other when Yugoslavia broke up, and they molded fiber/ceramic reinforced concrete to defeat AP rounds and some RPG's were even defeated.
-------------------------------
Our troops are using 'Gun Trucks' with ammo boxes of rocks or concrete out against the outside of the truck bed, and sand bags or ammo cans with packed earth behind them to absorb the shrapnel from the rounds breaking up in the rocks or bricks...
Works very well!
Military gun truck - Wikipedia, the free encyclopedia