even thou they share the same stroke, a 307 is not he same as a 327.
If you use a 307 crank in your 327 you will have to rebalance the crank.
If you use your 327 crank and resize your 327 rods and get replacement 327 cast flat top pistons that are equal or very close to the stock piston weight, you won't need to re-balance the crank. Thats a good deal.
The price is reasonable but nothing especially cheap about it. You can get your 327 crank re ground for the same price or less. You need to get friendly with your local automotive machinist.