Your '79 should already have a 4" cutout on the passenger side behind the grill next to the radiator, and there will be a 4" plastic fitting snapped into the hole. The stock air cleaner snorkel on most '79's once had a hose running to that cutout. There is a 2nd cutout on the driver's side, with a metal plug held in only by tabs in a couple of places. You can punch this plug out and put the same 4" plastic fitting on that side.
Cheap method - You can add a 2nd snorkel (from junkyard) to a stock air cleaner and connect both snorkels to the fresh air cutouts on each side. Its probably not quite as good a flow as the aftermarket kits, but its cheap if you can get junkyard parts.