Has the engine ever actually been broken in since "rebuilt"?
I'd say "drive it" for a while. Get a feel for the oil consumption, if any.
Check the PCV valve and hose at the back of the carb and transmission vacuum line for a show of oil. An intermittent puff of blue might be a couple of drops of oil getting sucked in from something like that.
It's also possible that valve stem seals may have dried up a bit after having sat for 4 years.
If the problem persists, I'd suggest that you pull the plugs and read them.
If you put a mark at the top of each spark plug base (and find the plugs to be oil fouled upon removal) you'll be able to determine if the oil is coming from the top (valve seals, PCV, trans modulator, etc) or from below (i.e. rings)
If it's running rich (fuel smell) it may be that some of the debris / sediment from the fuel tank might be working its way thru and interfering with the need & seat in the carb. Check & replace, if nessecary, the fuel filter while putting a couple of tankfuls through it.