I found a good deal on a new aluminum CO2 tank. The possible drawback is that it is for scuba. It is a 4.6lb tank and does not have a valve. Will this work for kegging?
If it's for SCUBA it's not a CO2 tank. You may be able to finagle a way to install a CO2 tank valve in it, but you will be hard pressed to find a vendor that will certify it and fill it.
A tank that small actually sounds like an SCBA (self contained breathing apparatus) not a SCUBA tank (self contained underwater breathing apparatus). These are used by firemen, or are at emergency stations in mechanical rooms for use during an escape of hazardous gases, etc.
Like I said, even if it were possible to adapt a CO2 service valve into that tank, it is unlikely that you would find a filling station that would fill and certify it for use as a CO2 tank.