well first what kind of car is it going in? also how much money are you looking to spend on this motor? the first thing i would tell you would be to get a 350 but i understand that this was your grandpa's car. would you ever consider pulling out the 305 and sitting it on a shelf, and buying a 350? and building it, that way if it ever broke or blew up it wouldnt be the motor that you grandpa had. but if you are dead set on the 305 we are going to need to know how much money you are looking to spend and what kind of motor you want, are you gonna want to drive it on the street, do you want a motor that is going to rev and make power at high rpms or a motor that makes low end torque, low end torque isnt going to be easily accomplished with a 305, i would build a reving motor
Tyler