Is it possible to convert??

Can't help on the coil overs. From the looks of it the springs are beyond weak. They appear to have a reverse arch and looks like someone added longer shackles to recover the ride height, the springs may not even be an A-body leaf. You could measure the front segment from the spring eye to the center pin and get a better idea. Me personally, and depending on your goals, I would look at either having the leaf springs re-arched or replace them and put original style shackles on it. I think it would be a lot easier and cheaper than installing a coil over system.