The A-body upper shock mounts definitely need to be reinforced if you do a coil over conversion. Good article on this in the most recent issues of Mopar Enthusiast magazine. They detailed a conversion to front coil overs that do not use a replacement K-member. Magnumforce also has a reinforcement bar setup for this as well.
I recommend you look into an AlterKtion front end from Reilly Motorsports if you want to use a replacement K-member. It's a great setup.