30 AMP home wiring Question

Get an electrician. I see problems with almost all of the advice given so far. A outlet must, in most states in the US, have a metallic ground connection back to the main panel, a separate non-locally-bonded white neutral cable, and a hot cable. You used to be able to re-mark cables with tape but that hasn't been allowed for a number of years, again in most states. Now you must use a indelible marker or paint. In some states, if a sub-panel is in a separate building with no metallic connection back to the building the main panel is in (like plumbing, telephone, cable TV or other electrical wiring) then a local bonded ground can be permissible. It is never permissible to either ignore local codes or to do wiring installations without a permit, regardless of if you own the building in question it's always illegal, as far as my experience goes. If you do it or not is up to you. If you can sort out the ground issue, you should be able to install a 50 amp style outlet but fused to suit the 8 gauge wiring, for 40 amps or 50 amps depending on the type of cable.

Brian