For anyone out there that has wondered aout the Standard length of a Challenger Drive Line with a 727 it is 45 25/32" long.  Just some info that I was able to stumble across thats to the knowledge of one of my buddy forum members.  

Thanks Goatheat  

The 1970 Challenger for some odd reason had 2 different lengths. I found out the hard way when converting to a Keisler 5 speed manual from a 727 auto (luckily didn't break anything). They (Keisler) has the specks for the 2 lengths.
Mike  

Depends on what rear end 8 3/4 or dana 60.

Goatheat:
I am refering to my experience with my 70 Challenger that has an 8 3/4" and was one of the first off the production line back in 1969 and shippped to Canada. Keisler Auto explained to me that VERY early Challengers had a slightly different length driveshaft when used with 8 3/4" rears (for a few weeks or a month they were produced that way). I don't know if it was as a result of engine being mounted further back a small distance or if it was something else. However, they discovered the difference when a few customers converted to their 5-speed had problems with the new driveshaft hitting the "Doghouse" of the trannie. Their driveshaft was "specked" to the factory length for a later Challenger (I believe it was a 71). So to make the story short, they mow ask when the Challenger was built and decide which length of driveshaft is appropriate for a conversion from a 727 auto car to their keisler 5 speed manual.
By the way, I love the keisler manual, It is way better than the old chrysler 4 speed, I can use 3.91 gears and still cruise at 70mph at 2,200 rpm.
Mike
 

Good info thanks.  

well I ended up finding one that hopefully will work for my application.  it was out of a 72 set up the same as my 73 will be.  I guess time will tell.