Taking my truck to emissions today, Need help!

[wldcat10]

Ok I'm taking my '70 to emissions today after I get out of work. I need some help or suggestions on what I should do before heading over there. Last time I took it, it failed the Carbon Monoxide part, it passed the rest. I have heard to run it for about 30 miles or on the highway so that the engine can get hot. I think last time it was my fault because I was in a hurry to get it done and went straight from my house to emissions (5-6 miles away from my house) and it failed. I have never failed to pass emissions except this last time! I was really surprised and po'd! So is there anything else I should do other than run it for 30+ miles to get it hot? I always put 87 in my truck, Should I put in higher grade of gas? Should I drop in a bottle of one of those gas treatment or "guranteed to pass emissions" into the tank? Any help/tips are greatly appreciated!