With a car like this, sitting for a long time, in unknown condition, before you try and spin the motor over, take the carbs off, with a long 1/2" ratchet, ( pull all the plugs first ), rotate the motor in the opposite direction it normally runs, while looking down into the blower.
Alot of times, hard shelled bugs and such will ruin a blower because it'll jam up the rotors. There are only just a few thousandths of a inch between those rotors.
I've had Junebugs cause a blower-flairup....make the pass down the 1/4, but really ding up the rotor lips....
I would, to be on the safe side, just pull the blower belt and care, fully rotate it, make sure nothing is inside there that isn't suppossed to be there, clean and wipe her out really good with a lint free cloth and alcohol. A great find and a great deal! Just be sure to check it out thoroughly!