In the old days, we didn't do the same cam run in we do now. But we also didn't have as much spring pressure and ramps were slower.
Remember what the run in is doing though, the cam is spinning, the lifters are spinning because they are slightly offset to the lobes. Meanwhile the crank is throwing a ton of oil at those surfaces, taking away heat and allowing them to burnish (metal on metal polishing with oil and heat) together.
It seems like it's loud and revving high, but 2500 is really nothing if you can keep it cool. There is no load, the load isn't coming off and on, and the oil is flowing well, so the engine won't mind a bit.
My recommendation is consider it starting over. Make sure oil and water is topped off, fire it, and just stand there watching the gauges and looking underneath for leaks. Get it up to 2000-2500 using the idle screw with the new fan, and maybe a big old house fan in front. Once it's fired, you can look at the timing with a light, or just advance it a little more, no load it'll handle a ton of advance. It'll get boring after a while, and it should. After 20 minutes, idle it back down with the idle screw, set the timing with a light, and shut it down.
It may be a little hot, and may even want to run on, but if it didn't overheat, don't judge it yet, it's a fresh motor, every piece has more friction than it will after break in. Get it out and see what it runs like and start fine tuning
