International arrival and internal departure on the same day, different airlines in Beijing Airport.

Both these two flights are located in T3. Yes, you need to pass through custom inspection. But the Border Inspection is not necessary. In general, the mimimum transfer time is an hour. Thus you have enough time. Don't worry.
Besides, the procedures are Flight Arrival - Transfer Procedures - Stamped on Boarding Pass - Security Check - Custom Inspection - Waiting & Boarding
Hope helpful!