found another 70 challenger,car is on a rotisserie,all metal work done,fully primed and ready for paint,440-6pack,727 and diff completely rebuilt but now i'm wondering how much it would cost to put a completely new interior in it?

Depends if you're going new or used. All prices approximate

If new, the Metro panels (purchased from Roseville Moparts) are excellent:

Door panels, rear interior panels and seatbacks - $1200
Dashpad - $700
Seat covers front/rear - $500
Seat foams - $250
Headliner - $100 (including insulation)
Package tray - $40
A-pillars - $50/pr for decent used
Kick panels - $50/pr for decent used
Carpet $120
Sill plates - $75/pair
Correct interior paint for metal trim pieces - $120/pint with the correct reducer etc.
Sunvisors - $75/pr

Seatbelts?

Labour on seat covers & headliner - $500


So about $3500 give-or-take plus GST

Less if you have good used pieces that will work such as door panels etc

More if you need everything including seatbelts, woodgrain for the door panels/dash etc.

I just went through this on my Duster, it AIN'T cheap!

I don't have the exact figure but if you do a top notch job and get EVERYTHING new or restored you can easily spend 5-6K on an interior. Even more if you are talking about farming out the steering column, foot pedals, heater box, e-brake assembly rebuilds, etc.

Personal real life example:

I stripped my own seats to the springs, made neccesary repairs, painted them, and delivered them along with my new Legendary seat covers ($1,080.00) to the upholstery shop. I elected to go with all new foam as well (nothing like a brand new interior that smells like a rotten mouse nest) so new foam and top shelf install job came out to another $705.00. Mind you that this is for a base model bench seat front and rear (plaid cloth inserts made covers more expensive than plain vinyl).

I bought a headliner from SMS ($200.00), door panels, arm rest bases, roof insulation kit, firewall insulation, under dash insulation, insulation clips, package tray, trunk divider, sun visors, tips, door panel clips, sail panel boards, bench seat hinge covers, glove box liner, from Dante's ($899.00) a ship flat carpet set from ECS (around $375.00?) seat belt restoration by Snake Oil ($800.00) dash cluster restoration by GCAR ($1,200.00) dash pad from BE&A ($200.00) NOS arm rest pads $150.00, etc. This does not include restoring the foot pedals, heater box, e-brake assembly, or the steering column or steering wheel, and I havn't factored in some misc. small parts and labor to install the headliner.

Adds up quick!

I agree with Scott - if you count the proper rebuild/restoration of dashboard, gauges, heater box, pedals, steering column etc. it's not hard to hit the $5-6K figure. Especially if you need rare, NOS fabrics rather than regular vinyl.

Basically, how nice/well-working do you want it to be and how much are you willing to spend?