I hope that I understand your question correctly, as the solution apears to be too simple. (You do state that it is an Inventor DWG)
Open the DWG, then "File, Save as" OR "File,Save copy copy as Template" Change the file type from "Inventor Drawing files (*.dwg) TO Inventor Drawing Files (*.idw)
Open the DWG file
Copy the Title block from from "Drawing Resources, TitleBlocks." (RMB, Copy)
Start a new Drawing.
Delete the Current title block, Listed Under Sheet.
RMB on the Drawing Resources, select paste.
It wil either prompt you to overwrite the current title block, or it will paste a new title block if it was named differently.
Insert the new title block as per normal.
Save the file as a template, or drawing file. (IDW)
Reg Autodesk Product Design Suite Premium 2014 SP1 Build 222 Intel Core i7 (email@example.comGHz) Windows 7x64 (Home) - 12GB Ram Nvidia GeForce GTX 560 Ti (1Gig - Ver:331.65) Please accept as a solution if it fixes your problem.