It will give a little, depends on what you are going after. It's not a bad job to just put a 460 in it. Trans will bolt up and the mounts aren't bad. Or you can bolt in a 400 and put a 4V on it and a mild cam.
It also depends on the carb, those one-size-fits-all Edelbrock units are not my favorite option....their off-the-shelf configuration may not be the best for your application. You might consider calling AED Performance and discuss
your situation with them