Help with light/heat set-up?

[sunflowercake]

I plan on acquiring a baby black and white Argentine tegu soon.

Since it'll be a juvenile, I plan on housing it in my 50gallon long tank for two or three months while I continue to build his "official" adult enclosure.

Here's what I have already for the set-up:
-the tank (obviously) (48"L, 14"W, 20"H)
-a 150watt ceramic dome (I do not have any bulbs yet)
-an undertank heating pad
-a climbing log on the left side (where I plan the basking spot to be)
-and a hiding spot/moisture spot on the right side (cool side)

However, I live in the northeast U.S. The house doesn't get warmer than about 72 degrees during the day. If we turn off the furnace, the temp. will drop as low as 60-65 degrees at night.
Is 60-65 degrees too cold for the cool spot?

If it is too cold, should I put the heating pad under the tank on the cool side, and make sure it's regulated to keep 70 degrees during night/day cycles? Or would I be better off just using a night time bulb (assuming it would give off enough heat to maintain that temperature)? Perhaps both? Blue bulb or red bulb?
And if I use this scenario, I'd probably have to go ahead and get the PowerSun bulb for basking heat + UVB + UVA, right? I'm just hoping that won't overpower the 50 gallon tank. I plan on getting a lamp stand to hold the dome above the mesh wire top.

Or if it's not too cold, should I just put the heating pad on the left side of the tank for heat, while getting a Reptisun 10.0 compact UVA/UBV light to put above it? In that case, what kind of night bulb should I get? And should I place it in the same spot as the basking bulb, or a different area of the cage?

Any help would be appreciated, whether it's a completely different set-up suggestion, light bulb suggestions, anything. And sorry for being so wordy. I've had smaller reptiles before like turtles and also some salamanders, newts, and frogs. But this is my first BIG lizard, and I'm dead-set on everything being perfect.

 

[Orion]

I had an aquarium for smaller Tegus at one time. I would not worry about the under tank heater since Tegus that live in the wild do not have under tank heaters and survive the cold night temperatures just fine, also the little one may try to stay buried near the heater and not socialize properly. One of the main things you need to worry about with the aquarium is providing enough humidity. I made a wood top by taking a 4 foot long pine board and cut 8 inches off each end and cut a circle just a little smaller than the diameter of the dome for the basking light but make sure you leave enough room to run a 24 inch long light fixture. It took me a while but I was able to find a small under counter mount at Lowes that didnt take up too much room so I could mount the 24 florescent along the basking spot. Paint the wood, so humidity does not penetrate the wood.Then put hinges on the 2 pieces of wood you cut off each end for access. I used 24 inch Exo terra Repti 10.0 and Sloar Glo for the basking lights. I am not a big fan of the compact florescents.