If the stock suspension is in good condition, you can just use it, if mostly good just replace worn parts with stock parts. Old e bodies handle pretty good, with disk brakes up front they stop ok.
Up grading the brakes to something like a new SRT has would cost about $3000
To put in a different K frame, and rack and pinion, At least $3500.00 and to get a 4 link or other rear end upgrade again, 3 0r $4000. These numbers are for parts only, if you need to hire someone to do it, double them.
Most projects start by taking the car completly apart, assuming it needs a paint job and some metal repairs. Once apart, media blasting to remove the old paint to start fresh. A complete media blast job, will cost about $2000, plus the cost of getting the car in a sealing primer a few hundred more. Body work can be nothing if the car is perfect, and $10,000 if lots to do, a paint job by a professional shop, could be anything from $5,000 to $25,000 depending on which shop and the details.
Once painted, it gets put back together, often you'lll spend several thousand on smaller stuff like weather stripping and screw kits, door sills, and might need new glass and or hardware. Interior replacement seat covers aren't too bad and can be done by a good handy person, although headliners give most people fits.
Then its details and drive train....
Someday your done, a beautiful old Mopar loved by many including yourself, The time invested will likely be measured in years and money... more than you really wanted to spend.
I'm not trying to discourage you, in fact just the oppisite, just know what your getting into, and enjoy the build up process, the dirty finger time.