I wouldnt mess around with heat vines or the like. Like I said earlier, keeping things simple is often the key to success. I really like to maintain one heating element, and one temperature. Insulation is going to be your friend here with this issue. You can head to home depot and they have a plethora of options for insulating. You could buy some actual insulation made for houses, or simply get some styrofoam slabs and affix it to the sides of the enclosure. They also have spray insulation in small canisters.
This is why AP T8s are so popular. They have 1/2 inch PVC that really holds the heat great.
65 deg is considered pretty cold for a snake enclosure to be in, but can definitely work given the proper insulation.