Welp, think I figured it out. Temps are steady at 88-90 on warm side. I tried taping the probe onto the case and putting the flewxatt over it but it wouldn't sit flat so I decided to tape the probe on the outside.
Since it will be sitting on the floor I might use a piece of Reflectix underneath; it will help keep the temp steady and provide some noise insulation too.
No lighting installed, and not sure if any is needed; it will get indirect sunlight during the day.

The cage has a strong rubber/silicone smell so I'm going to let it air out for a few days and hope the smell goes away before introducing the snake to his new home. I think 1 brick of coco husk will provide a good layer of substrate.
There's plenty of room inside for 2 hides, 1 water bowl, a piece of cork flat and a branch.