Good question. In that moment, I like to have him around 2,300 or so. Enough for him to be above Piccolo, yet still be below the Masenko. Piccolo's reaction there is basically the same as it was when Gohan hit Raditz and destroyed that mountain. The type of reaction that says, "I can't do that shit". I really don't see Piccolo being capable of that at his level.
We know the two big Chi powers are Gohan and Piccolo. This might imply there's no significant difference between them at that point.
The start of Gohan's rage quickly gets the scouter's attention.
Gohan's power seemed to quickly jump to 2,800 right as soon as he got in the Masenko stance. That tells me his enraged level prior to that likely wasn't that far behind.
Based on everything we know: Masenko>Gohan's Outburst>Gohan's kick
Another thing to take note of is that Vegeta's scouter was off for awhile, so Gohan's power could've been around the 2k area once he stopped acting like a bitch. Gohan was about to attack Nappa before Piccolo got elbowed, after all. If not in the 2k area, slightly below it. Well above 981 at the very least.