Welcome 6chevy5, sounds like your getting into a faily soild project. If your putting in the engine from the impala then why dont you use the tranny also? That is if the 3 spd in the truck seems to be frozen up. Be sure to check the linkage from the column to the tranny to see if its binding. If thats ok then it could be the tranny not letting you shift through the gears because of being wore out. As far as the V-8 going into the truck youll need V-8 motor mounts to accomplish this.
