Correct- simple bent aluminum strap. Some add strips of old bicycle innertube or waterbed patch material to protect the aluminum tanks
In a stock Pantera, there's two whole sheet-metal structures up front, on which each front-mount fan rests. The fans & structure interfere with leaning the new radiator few into their space. Yours seems to have been already removed.
The plastic fasteners incuded with the Flexilite, whatever they call them, do in fact damage radiator cores. The internal tubes are only 0.005" thick in brass radiators, and 0.012" thick in aluminum radiators- not very tolerant of any kind of physical contact or load.