Gday Shane.

Your 307 is a large journal 2 bolt main, 307 only come this way.
You could put a 383 crank in there but you would need custom pistons cos of the bore size.
You need a 327 L.J. block or a 350 block to make 383 cubes.
4 bolt main depending on the power you want.
Thanks Sam
By the way i live in Victoria