This is the 305 I just pulled out of my 86 Chevy Pick up with 340,000+ miles on it . I changed oil and filter every 3500 miles. Look at those intake ports talk about clean and the lifter valley was clean too. When I changed oil I'd throw in a can of STP sometimes, old timers used to say pour STP in and dig it out later. The motor is in the shop now and I might get lucky and just need a re-ring and bearing job no bore if the taper is OK.