I had to pick up another 88 Gt to replace the one my son had that got totaled by an idiot a few weeks ago. I started pulling parts from his and started the restoration on the new one. When I pulled the valve covers off of the one I just purchased I noticed it had 1966 289 cast iron heads on it. It also has a stage 1 TF cam in it. What would be the purpose of putting 289 heads on a 5.0L? Do you think it will improve or hurt the hp on this car?