you have a pacesetter and stock nikki carb? Now the truck is running rich- o2 sensor is out, or accelerator pump in the carb is trash, or a combination. I would guess the carb is shot. Weber would be a good fix for that....
I would take the time to redo the timing before you spent any money. Unless the belt is bad its free to check and correct that. The Dis should not be all the way forward. That would be my first place to check.