Every engine is different. The BEST way to know what it needs is a wideband A/F gauge. My 2165 is very happy with 1.40 main jets. If the heads are really efficient, and they are, a 1.35 might be perfect.
IMHO Panchitos are too small for a 2276. I'm quite sure you have plenty of low end torque, those heads are great for that. But they are a choke point, just like too small carbs or too small exhaust. For me, the max size would be a 2 liter. You're limiting power with those heads.
The engine isn't finished yet, but the CB heads I'm using on a 2276 build flow 30% more than Panchitos, yet retain a smallish intake tract to keep torque high. 30% is quite a bit more flow.