My buddy put an American Power Train TKO600 kit in his Fury and the kit less clutch arrived for a cost of just under $4,500. So whatever the going rate for the A855 is (which seems to be somewhat closely kept) would be the difference assuming you have existing factory 4 SPD components. APT can send a kit out the door tomorrow. So for an E or B body a kit is available if you are not set on a drop in solution.
Last I recall the Passon 5 speed is "currently" $4995, for that you get, transmission, shifter assy, and speedo cable
You'll need to procure all the other manual tranny conversion parts if you don't have them, or your vehicle is currently an automatic