I don't know which committee Grassley will be chairing in the 109th Congress, but I don't think it will be Finance.
Sen. Grassley is already listed as the Senate Finance Chairman. He is expected to chair Judiciary after his term limit as Chairman of Finance is up in four years.
Sen. Grassley's credentials as a conservative cannot be challenged.
http://finance.senate.gov/
http://www.insightmag.com/news/2002/11/12/Politics/Iowas.Main.Street.Republican-308296.shtml