FWIW ... here's the answer I got from TST sales mgr:

The difference between the 507 RV and 507 SCE is that the 507 RV is designed for RV’s, and small trailers. The sensor has a user replaceable CR2032 battery. The SCE is designed for the Commercial Market, 18 wheelers, and large trucks. The SCE Sensor has a sealed battery that is not user replaceable, and is designed to last 3-4 years.

I would recommend the
TST-507-RV-6-C, and 3xTST-507-RV-S2 for your application. This will give you the 12 sensors you need.