Greg,
Both 307 ans 250 shares around the same compression height. As much as the 283/230/153.
The only deal is that the gasoline 250 normally have dished pistons, and the 307 ones are flattop. You mentioned forged race pistons, how about their head? Is it a flattop? If so, go for it. If domed, pay close attention to the dome interfering with the head. If domed, You can bore the block and make a mock up assembly to check out what should be done in order to avoid piston/head contact. And remember one more detail: Flattop and zero deck height should provide more than required compression ratio. Don't go wild on compression or You'll be tied to a engine requiring high octane gasoline. Or useless in normal use.
