Radiator Over Flow Tank for a 66 barracuda

I am looking around for over flow tank ideas and suggestion. I plan to do an autocross at the end of the month and the rules state that over flow tanks are required

66 barracuda with a 22 inch radiator

I have found some very narrow tanks; 2"x10" that might fit in between the grill and radiator support. Or remove the horns and strap it beside the radiator in that gap (which would probably fit and have areas for straps)

What is everybody else using? And picture would be great

I will not hack up the car