I'm running stock air filter, 70A carbs, laser headers and Mac mufflers. 142 mains and 40 slows, 1HE needles, 6mm float height. At sea level, she ran over 100rwhp with an A/F ratio just at or above 13.0:1. 145s would be fat, especially at altitude and/or on a warmer day. Would the K&N justify 145s with your exhaust? Maaaaybe. With stock exhaust? No way, Jose.
I'd start with 142s.