So great story about this flip *note the sarcasm*. The guy message me the next day, and saying the temp on the grill was only getting up to 350. I told him that I'd drop by later that week to troubleshoot.
I started gathering extra parts (burner tubes, regulator, thermometer) to test on my grill at home to make sure it worked before bringing them over. I don't have any new burner tubes, so I was using existing tubes from other rehabs. I picked the ones that look like they are in decent condition, and they won't fit in the firebox with the regulator (too short). I measured the firebox, tried different tubes, tried different regulators. I got so frustrated, I called it a night and was questioning my abilities to troubleshoot these grills.
The next night, I picked up from where I left off. I decided to pull ALL the burners tubes I had, regardless of the condition. That's when I measured them, I just happened to grab multiple tubes from an old Silver B, and that's why I couldn't get anything to fit. I guess I was too tired the night before to consider this. I tested everything, and I now have a regulator and burner tubes that I know work and get up to temps of 500+.
Regarding the thermometer that I included in the flip, I originally bought a new one on Amazon,
GASPRO Accurate Thermometer , and condensation got behind the glass, so I sent for a replacement one. It didn't come in time when I had to deliver, so I grabbed what I thought was a clean/decent looking one. I actually think everything is fine on the grill I sold, and the thermometer I included is faulty (i'll find out tonight), but now I know better for future flips.
Check EVERYTHING so I don't have to make another trip.