Do like Shawn said, use some thin wall square tubing and replace the wood. I helped a guy turn a 4 dr. chebby sedan into a 2 door chebby sedan once, wasn't too bad of a project. We move the post between the doors back, then used the fronts of the rear doors to add on to the rear of the front doors. Enlarge the side window opening and presto-chango, ya got yerself a 2 door sedan. Once the posts are where you want them chop about 3" out of them and get the roof down to a respectable level.