I believe Napa 615-1606 will work...I think other stores use the same number...it is 87" long so check if that length works...
Note that the ATP Y-803 is 83" long....listed for a lot of cars including a 67 Charger. Has the 5/8-18 threaded connector on the speedometer end which fits the Autometer speedometer. I ordered this one
NOTE! Y-803 was a bit long, got against a collector and fried itself.
I then tried Y-804 which is 63" long. I was able to run it down the bellhousing and along the tranny thus avoiding the exhaust. Looks to be a much better fit to me.