No such thing. If it were a cop car engine, it would be the same as a HP engine in other cars. (Like a E-58 engine for example)
My question is: other than motor mounts/ k frame, driveshaft, radiator and a bigger rear end, what else will i have to change to fit the 360 in my duster?
The drive sahft may need to be shorten a tad if you go from a 904 to a 727 and then a bit more with the rear upgrade. A 8-1/4 is good and cheap while a 9-3/4 is excellent, strong as heck, but a bit pricey.
The rad is a great idea, even more so if your pumping up the 360.
Will i have to change the tranny crossmember? Also what kind of price range am i looking at for the parts needed
Trans cross member can stay, correct mount to be used if need be for trans change.
Total cost of this is something you can mostly figure out. It would be based on psrts only that you choose and then remember the small things like saw blades and gasket sealent. Maybe tool rental? IDK whatcha got.