Best Practice to load HR payroll data to Project Costing if HCM is not being utilized

We're implementing A/R, BI, CONTRACTS,  PROJECT COSTING, but we're not using HCM.    Currently, payroll data are loaded to GL through a flat file.  What is the best way to load same summarized payroll data to Project Costing.    We tried the Cost Collection, General Ledger,  use options Project and Journal Date option but the amount is missing from PROJ_RESOURCE.  Any feedback from the group will be greatly appreciated.

Thank you.