One pipe may be different to tune than the other. I use the 2630 with short header and like it. The key to the 353 motor is gearing and the split from 1st to 2nd. I normally run about 2.3-2.5 final drive split and also make sure the 2speed is shifting correct. I use this pipe on tracks like Ft Myers, which is bottom and mid range and also at Kissimmee, which is top end. I do not think you need the 2602, however if you like to have choices, it can not hurt. However it is not needed.
Regards,
DJ Apolaro