Manual Transmission

[msbaugh]

Not all 440 crankshafts will be drilled for the pilot bushing... Before you start buying stuff make sure your 440 will even take it. Yes, there are special bearings to help but this requires hacking the input shaft down on the manual.
I was going to do the same thing until I hit that hurdle. I ended up just fully building up the 727.

Everyone's right, looks better, more fun to drive, more nostalgic etc.
But.... The automatic is faster and more bullet proof if you build it right 

[HP_Cuda]

You will need to look for an A833 that is setup for B&E bodies. Meaning it has both the forward and rear mounting points on the tailshaft.

4 speeds are too much fun and bring more $$$$

[Chryco Psycho]

Rather than trim the input shaft shorter you can also bore the rear of the crank for clearance \& use the Dakota roller brg for a pilot .

[Sinatra]

thanks for the good info, so any  a833 with the rear shifter mount will fit my 73 challenger ?

Yes.  It will have two shifter mounting provisions, one in the front and one in the rear.  An A-body (short tail) won't fit correctly and shifter linkage would be a nightmare.  D100 pickups through I believe '87 were available with the A833 overdrive transmission that has the rear shifter provision.  You'll need to carefully mark and drill it, though, since I've not come across one yet that had the rear bosses drilled and tapped for the shifter mounting plate.  Overdrive truck transmissions are easy to spot; they all have an aluminum main case with an iron tailshaft housing, and the front lever on the side cover is installed pointing down.  A stock 3-4 shifter rod will need to be modified a little to work with it.

On the depth of the crank bore for the manual transmission: 
I've seen it done with the Dakota pilot bearing used as a drill guide to keep the 3/4" bit oriented axially; the tip of the bit will center itself in the far end of the existing bore.  The guy then went back with a slightly larger pilot-point drill to enlarge the hole for additional installation clearance.  He also threw out the bearing he used as a guide and got a new one, which is a must as it will have shavings in it.  This was done under the car, and though I don't recommend this procedure, it did work for the guy.  If you're extremely patient and precise by nature like he was, though, you might pull it off.  Might.
Cutting the end of the input shaft short enough to work with the undrilled crankshafts has no functional drawback, even when used with a factory 4-speed crank, but it sure hurts the value of the transmission.  Even though I know it doesn't make a difference, I still offer sellers considerably less on a transmission modified in that manner.