327's are great motors , and they like to rev . They were small main bearings prior to 1968 , and then they had larger main bearings the same size as the 350 for 68 and 69 .
It will physically bolt into the Impala/Caprice using the engine side mounts from your car .
Make sure you use the right flexplate for your starter , they come in 153 tooth ( starter bolts right across from each other ) and 168 tooth ( starter bolts staggered ) , and that it has the right bolt pattern for your torque converter . Can more than likely use the one off the 305 .
Use a cam intended for the gears and weight of your car , its all to easy to overcam the motor and then the cars performance is lacking .
It may not be emmissions legal if they check the block numbers in your state , even though once all the stuff from your motor is on it , it would look like your old 305 . If they don't look , or don't care , then your good . A rebuilt motor in good tune with your 305 stuff on it could burn cleaner than your worn out 305 did .
You may be able to find a crate motor with most of what you need, and then add some parts form the junkyard to fit up all the accessories. Some machine shops can drill extras bolt holes and such if needed.