Id expect to see some degree of smoke like you're seeing on a 'free' engine like that... I ran a qt of MMO through a Studebaker 289 both in the oil and the gas and was amazed how much cleaner it ran. It had sat for years like yours and was close to 1K miles on odometer.
It went from mozzy fogger to misting tailgaters like your describing. It might clean yours up enough to get you in the 1qt/tank range... for free I'd live with that and be glad I had a built in tailgater 'back off' tool to to use on unwelcome commuters riding my bumper.
