You need a BIG box and LOTS of packing material. Dimensional weight is how they'll charge you on an item like this and the prices can be ridiculous. IIRC you're in the San Francisco area. The weight and dimensions I used are larger than they'll actually be.
USPS won't touch it. Too big.
FEDEX? Lowest quote from them from the zip code I used (94129) to me (75089) on an estimated 40 lb.box w/dimensions of 60x24x24 with a declared value of $500.00 is $214.44 (at their slowest service)
UPS Ground? (must be 60 inches or less to avoid "special handling" charges) with the same figures as above: $268.84
I think the most inexpensive way to go with something this size may be OTR freight. There are so many of them I didn't research it.
Greyhound is an excellent alternative for shipping large items at a decent price.
Their size guidelines:
"The maximum weight per package is 100 pounds. The extreme measurements of length, width, and height shall not exceed 30" x 47" x 82"
Definately enough room for a dashboard box!
BUT, a drawback exists:
"Auto parts will need to be tendered with OEM packaging.If manufacturing packaging does not exist we will accept at the shippers risk or at no declared value.
Shipments more than 48" in length could take up to 30 days in transit due to space constraints."
There are a few other guidelines as well. Check http://www.shipgreyhound.com/faq/#packages_1
for more details.
I got a quote for shipping on Greyhound for the size and dimensions listed above from San Francisco to Mesquite (closest Greyhound Station to me) $73.00
The shipment *may* take as little as two days. You will have to take it to the bus station and the buyer will have to pick it up at their bus station. The savings is worth it IF the package arrives undamaged. I've used them before and never had a problem with damaged freight.