Dillon 450 is a 4 station progressive press without removable tool head for dies and came with manual powder/primer feed attachments and manual shellplate advance.
Because of manual powder/primer feed, progressive loading on 450 can be slow but you can upgrade both with a conversion kits from Dillon.
I have 2 other progressives (1 turret and 2 single stage presses) so the 450 is used dedicated to a caliber and solid top works like a single stage to give me precise OAL consistency control which I like.
450 to 550 conversion body with removable tool head will cost you $95, auto powder measure $89, auto priming attachment $86, auto case eject $60, low primer warning kit $26. The upgrade will run you around $350 but you can sell the solid top body to recoup some of the upgrade cost.