If you plan to keep the 307 I admire you, since it`s not a run of the mill 350.
I would check the pistons, if they are factory pistons try your hardest to keep them, as all the aftermarket pistons have .020 off the tops that kill the compression and quench, the factory flat top was the ticket, since the only piston you can get with the correct compression height is the forged piston, and since a 307 is a uncommon build, they cost over $400.
I would use heads off a 305, the 416 or 601 casting head will work well and keep the compression ratio within a respectable ratio, a light bowl port job would be of help also. The edelbrock cam will give it great low end power, make sure you add a double roller timing chain.
The 307 is a small block chevy, and it`ll respond to mods just like the other small blocks will. If you want more cubes, take the 307 crank and slap it in a 350 block, you`ll have a 327, just use 327 pistons.