6-v8 k-member kit
Here is a link to Schumacher:
http://www.engine-swaps.com/
There is also a thread on here about a kit from Summit at a good price. I didn't read through it all, but it might be worthwhile finding it.
You'll probably need to change the driveshaft if you swap from 904 to 727 and/or change rear ends because of the length, slip spline and possibly rear end yoke.
Found it!
http://www.forabodiesonly.com/mopar/showthread.php?t=156115&highlight=summit
...but as noted in the thread, it's for a '72 & older k-frame. Schumacher has the '73 & newer kits, but a lot more expensive.