Yes, You can throw a 307 crank in a 350 block and it makes a 327.
With 5.7 Rods you would use 327 pistons with the 1.675 Compression height.
It would depend on the combustion chamber size of the heads. If they are
64cc's a flat top design would work nicely on pump gas. If the heads are aluminum then you can run higher compression on pump gas due to aluminums ability to dissipate heat quicker.
You can even use the 307 crank in a 1 piece rear seal block, however you'll need the 1 to 2 piece seal adapter. However if you go this route with the
307 crank, I recommend you have the crank balanced since the 327 used heavier pistons than a 307.