yes a 283 .125 over makes a 301.6 <302> and you will need 302 pistons. make sure you have it magged 1st then have it bored if it checks out ok. i have done a few of these motors up and have learned from others who built them alot in the 60's and 70's but make sure it checks out ok on the wall thickness. and dont let nnybody fool you, if done right it wont overheat. i have a 160* stat in my car it goes to 160 and stays im actually having to change to a 180* because it wont warm up! also the 2 bolt main will be just fine.. whats are you going to use this motor for? strictly racing? street driving? what kind of car are you going to put it in?