It could depend on the type of clutch and SFI spec of the can used. I would think an SFI can ordered for a single disk setup, with the clutch fork window placed in the stock location should fit pretty well.
On the other hand, something a little different, like a dual disk setup can cause headaches. I converted a small block car from a single disk clutch/Jerico 4-speed setup, to a dual disk/Liberty 5-speed setup. Every thing was different, the SFI dual disk can required a special smaller diameter flywheel....which required a special offset starter.....which required new mounting holes in the mid plate, etc, etc.