According to specs the stock lancer Tamiya body is 17.5" long and 6.9" wide. HPI Impreza is 17.5" long and 7.5" wide and that's for the 190mm body. You can make virtually any body fit anything you want although body modification and or chassis modifying may be needed.
So it looks like ya may be a little wide going with the HPI body. Wheelbase shouldn't be too much of a problem, I'd be more concerned about overall width of the body.