IMO the aftermarket has been very serious for brand X for over 30 years now. Are you just now noticing?
I built a 632 donovan block with pontiac big chief heads on it back in 1992 that made 1200 hp injected on alky. Then had a serious N2O system on it.
There was no way to go that fast with 440 stuff then just like now.
I did switch back to mopar when I went with a brad billet hemis.
Not trying to make the small block guys mad but, after those motors above the 340 I built most recently is like a go cart engine power wise.
I've built some serious motors.