The head is just the pump part. You'd need a frame, filters, motor, drive parts, plumbing etc.
The Daveys were just about only made to gov contract, and have recently been surplused in large numbers. They were extremely expensive when new, so new parts are also very expensive - if you can find them. Davey isn't around anymore, but another company is still making them. They also have a reputation for being not-so-great compressors.
They are big compressors, bigger than most of use need, and take a lot of power to drive.
Most of the parts you find on the civilian market come from cannibalizing compressors, so the most needed parts are often the hardest to find. Daveys can be a great deal if you can get a deal on Gov Liquidation on a low hour surplus one in near-running condition with all the necessary parts, including the filters to produce breathing air.Then you can run it until it breaks, and and if its to expensive to repair, part it out. Otherwise, they can be real money pits.
Bargain Marge on eBay often has Daveys and some parts. You can see what a bare head looks like on her website.
I don't know zip about compressors, Is a head an entire compressor?
Anyway, just wanted to let folks know as I do know fill compressors
go for big bucks.
PORBEAGLE