Step 1: Procurement and Parts
the mack truck bulldog hood ornament is available for purchase on ebay or online
I purchased it 6 years ago at a tour of the mack truck factory for 30 dollars at the time. it might also be a good idea to find a big scrapyard and check.
i used 3mm (aka T1) bright led's check mouseror digikeyfor the brightest ones available for the color you choose. 5mm led's would be too big and look dorky. its also good to use clear led's so that when the eye's are off they look like part of the silver structure, not little red dots. resistors can be purchased at radioshack or along with the order.
Current Limiting Resistor
the resistor value you use is dependant on the led used and the power supply for your vehicle. for an led with a vd or forward voltage of 2.6 volts and an id or forward current of 20 milliamps (see datasheet image) and a vehicle with a 12v supply here's the procedure for determining the correct resistor value
(vehicle voltage - vd) = vdrop so:
12v-2.6v= 9.4V= vdrop
using R=(V/I) substitute values in place
R= 9.4V/ 20 ma = 9.4/ .02
so R = 470 ohms
the power dissipated across the resistor is calculated from P=IV
.02*9.4=.188 Watts , so a 1/4 watt resistor (common at radioshack or real electronic parts store) is ok to use. chances are a 1/2 watt resistor might be better suited as the resistor wont be able to dissipate much heat into epoxy.