All Classified forums require a Site Supporter subscription. It is only $25 per year and you can buy and sell whatever you like on the forum. To become a Site Supporter, go to Your Profile and select "Paid Subscriptions."
Only a boss can pull up to the gas station and hog two lanes at the same time. Inside the frame rails is not practical, you have the driveshaft and exhaust. Either stock locations or blazer tank conversion would be the most logical place.