ok you can sleeve a 400 barrell BUT the head studs are different so then you have to machine a 400 head to make it 490 and a 400 barrell stud patten is narrower too so that it wont bolt up too 81 cases.and it think he said the transfers were different,you can sleeve a 400 magnum engine to 490 and do the head im going on friday so i will get him to write it down and put it up here then any way i told you on the phone today after i rang him