Chevrolet Express:

Can 2 valve cover hoses be routed to a single vacuum port?

Depending on the car, engine and the vacuum hose routing to the type of vacuum port you want like manifold vacuum or ported vacuum (older cars). There are vacuum tees that are sold in different sizes that may be used if available in the hose size.

It would help if I had more information on the type of vehicle like the year, engine size, make and model. The more information you give  me the better I can help you.