340 advice

Hmmm...Rebuilt 35 years ago, driven 50 miles, parked and not run in 5-10 years.
None of this adds up. I’d figure the engine and possibly the whole car needs going thru.
If you decide to turn the engine over, leave the oil in unless it’s dirty or milky, spray PB Blaster on the rockers and inside the cylinders, leave the spark plugs out, spin up the dizzy, turn over the motor, (make sure nothing weird comes out) then put the plugs back in to see if she’ll fire up with fresh gas.