Hello.
As a motor, not much if it's been sitting on the floor for 15+ years.If it actually is a hipo, it would have some parts that are worth a little bit though.The block should have the casting number C5AE-6015-E on it.The main caps are bigger than the standard 289 caps and use 3/8 bolts instead of the normal 5/16 for a non-hipo.The heads are different also.They have screw-in rocker arm studs instead of the pressed-in.The springs sit down in little pockets instead of on a flat spot.They also have either 19,20 or 21 cast into what would be the front outboard corner of the D/S head.Here's a couple of pictures.Also the balancer is 1 13/16 thick instead of the standard 1 inch on a regular 289.The hipo fan,carb and distributor is different.If you have all of that it would be worth more as parts than as an assembly that is little more than a boat anchor.Hope that helps.
1966 Hi-Pro 289 engine 
