Need Info on slant 6 to V8 swap

HI, and congrats!
I recently did the same thing on my '64 so I may be able to help a bit.

your questions in order:
Q) 1. Do I have to change the K member? I hear you can buy a motor mount kit from Schumacher instead?
A) the K member on all early Darts and Valiants are the same /6 or V-8, you will need V-8 motor mounts, the stock ones are fine, I had to do a little work since I went with a later model 318 and somewhere in the '70's they changed the tabs on the block. you will need mounts from 1964 through 1966.
Q) 2. Do I need to change the torsion bars?
A) no, the /6 is pretty heavy, mine sits the same with the V-8 as it did with the 6. if you want to improve handling you can change the torsions but in general the stock ones should be fine.
Q) 3. It has 9" brakes, what do I need to change to 10" drum?
A) to change to 10" brakes you will need the drums and backing plates and everything between (shoes springs wheel cyls. etc.) this goes for front and rears. I went to the larger bolt pattern and disc brakes off a 1973 Duster to do that requires a little more stuff, if you want I'll give you a list of all the parts you'll need.
Q) 4. Is the steering box the same as a V8, I want to send it to Steer & Gear to have it rebuilt cuz I found a floor shift column and want to make it auto/floor
A) the steering boxes are the same, there are power units and non power. some headders will not allow for power steering, make sure you decide before you commit. there is usually nothing wrong with steering boxes, my advice, if it ain't broke don't fix it. inspect it, clean it up and put it back.
Q) 5. Do I need to find a V8 PS Pump or will the 6cyl work?
A) yes you will need a V-8 pump, you will need to make sure it is compatible with your setup. if you go with the old style cast iron water pump get a pump and brackets compatible with that year. I went with the aluminum pump so I had to have a newer style pump and brackets. also test fit the hoses to make sure you have what you need there are several ends on the high power hose based on the year. both ends vary, make sure your hose fits the box and the pump. the fitting on top of the box is changeable, but don't take out the two bolts, just the fitting on top.

here is the link to my post, you might enjoy reading it:
http://www.forabodiesonly.com/mopar/showthread.php?t=71831