I have a 70 challenger w/ac and a 71 dash with rallye cluster and no ac. It would be cool to have the tach in the dash, so whats different besides tach wiring harness? How different is the wiring harness? Any other issues I might have like defrost ducts? What about the dash frame? The car hasn't ever had air since i've owned it, so that wont be an issue, plus I like the look of the dash pad without vent holes. Thanks

So are you looking to change the dash pad also? If so remember that the 70 is a 1 year only pad and the 71-74 pads are the same. The 71-74 will fit but not look correct for a 70. The best thing to do if you are going to make the swap is just switch the whole deal-dash frame with the pad gauges and wiring harness all at the same time together. It will be a lot easier that way. There are 4 bolts,2 in each vent, then the 2 on the kick panels. Unhook the wiring bulkhead from the firewall and all wiring from the kick panels,headlight dimmer switch, and heater box/cables. Take the pillar moldings out along with the upper window trim. Then lower the steering column and take the dash out. It sounds like a lot of work and it kind of is but less trouble overall. Hope this answers your question

Wiring will work with a couple simple mods.

https://board.moparts.org/ubbthreads/show...&PHPSESSID=