Yes you can. Intakes, heads camshafts and exhaust can all be upgraded for performance. You can use some of the 302 stuff as well if you use the 302 firing order. But a couple things to keep in mind with the original motor. Some sources say the 260 is an underbored 289, it’s not. If you try to bore to a 289 you’ll only create a big heavy boat anchor. The 260/289 engines are obsolete and some stuff, particularly 260 only, can be hard/expensive to get.

But before doing anything think about what you want to use it for. Stock is best if what you want to do is create a factory car. Upgrades to a create motor, which will cost about the same as a complete rebuild, don’t hurt value really. And once painted it’ll look the same under the hood. There will though be costs associated with going from the 5 bolt original block to the current 6 bolt and connecting to the transmission, plus probably cooling mods either way.

Best advice, look for guys who are stock and guys who are modified and ask about their reasons and what they get out of the car.