289's are a good motor, from the factory the hp was rated at 271 horsepower. More power means way more bucks for trannys, converters, rear ends, etc.etc. etc. A nicely freshened 289 will do great in the Ranchero, if you have some extra bucks, get it balanced and go to a 2000 stall converter and a shift kit. Your plan is very sound, do what you can afford to do and keep it as a driver. Congrats on having a brain and using it !!!!!