I have towed 5400 with my access cab with no issues. But, and a big but, I have towed with tow trucks for 30 years and I have much experience. It handles the weight fine, no sway or excessive issues with the brake controller. Now without it? No way. So towing your 61 Bubble is not an issue if the weight distribution is correct on the trailer, hitch and truck. That being said, I recommend a spread axle trailer, aluminum if you can with steel undercarriage. Carson and Mirage build them. They are worth the money. Especially if you like me, and tow other people's crap all the time.