Yes, the VR-115 or it's equivalent is the usual choice for the '79 and older charging systems. You cannot use the regulator Bill linked to on your '78, it is the wrong kind. It is for the '80 and newer charging systems. When the TCI electronic ignition was added, the way the brushes were wired was changed. This was 1980 in the U.S. market, maybe a year or two later in some other markets. The earlier system on the points models grounded the inner brush full time through it's mounting screws and power was sent to the outer brush by the regulator. The regulator switched this power feed on and off to control or "regulate" the charging output. The later TCI equipped bikes were sort of opposite to this. The inner brush was fed constant switched power from the main harness and the outer brush was fed the ground by the regulator. This ground was switched on and off to control charging output. So, that means two different types of regulators were needed/used. The early system uses a power switching regulator. The later system uses a ground switching regulator.
The VR-115 is a power switching regulator and what you need for your '78. That VR794 that Bill linked to is a ground switching regulator and won't work on your '78.