Will the distributor from a 1986 chev half ton 305 fit 1989 engine?

No, a distributor from a 1986 Chevy 305 won't directly fit a 1989 Chevy 305. While both are 305s, GM made changes to the distributor design and possibly the engine block itself between those years. The mechanical components, shaft length, and even the electrical connections might be different, leading to incompatibility. You'll need a distributor specifically for a 1989 305.