$125 US plus shipping. Right.
So I decided to kludge this together for my brother's 40th birthday.
Bonus: you don't need to weld a thing! Although I'm a welder, I like the idea of the gears and the chain suspending each other. Besides, if your car used a belt, you wouldn't be able to weld them, since the belt is made of rubber and twigs and cat pelts.
Step 1: Parts
Clock movement kit with hour and minute hands ($8.00 US online) - This one has a 5/8" shaft and Maltese cross hands.
AA battery (depends on your clock movement) ($1.00 US, or less)
second hand for clock
clock's wall-mounting bracket
paint(s) and primer of your choice - spray paint is the easiest
masking tape and razor blade
nail or screw from which to hang the crank gear (the smaller of the two gears)
1/2" to 5/8" thick spacer for the nail or screw (to offset the thickness of your clock movement's plastic case
self-adhesive numbers or dots
Step 2: Tools and supplies
wire to hang chain and gears to dry
latex or nitrile gloves
clean lint-free towel or rag
wax/grease remover for paint prep, such as DX-330
large washer, stainless - to tighten clock shaft nut against face of cam gear
bushing - to center clock's shaft in center hole of cam gear (11/16" O.D x 5/16" I.D x 1/2" tall in my case)
paint - I used Rustoleum's Sunrise Red, gloss black, and Plastikote's clear gloss spray cans
wax paper - to set clock hands on for painting
heater to dry paint
clean brush to degrease parts
hammer to drive the nail into your wall