Methods and kits for assembling a flow cage assembly are provided. The flow cage assembly may be used in a traveling valve, a standing valve, or a top plunger adapter of a downhole reciprocating pump. In some embodiments, the method comprises assembling a body, a tubular insert, and a retaining element such that the retaining element forms an interference fit with the body and thereby securely retains the tubular insert within the body. Top plunger adapters are also provided, assembled from embodiments of the methods and kits.