I would recommend to NOT put a chevy motor in your challenger, that is just sacrilegious! I would get a wrecked ram pick up with a hemi and put that motor in it. For the trans, use a 518 (46RH, out of 94-95 RAM and others). It will cost a little more to get the him in but it is mopar and a HEMI. Then sell the rest of the parts from the truck to cover your costs. Plenty of threads on here on forabiesonly.com about the swap.
If you still want to put a chevy motor in, there might not be a lot of people who have done that (luckily) and you would probably be on your own. People will be
about that too... then
do the right thing, use the hemi.
For the trans, go to the trans section and read the A518 for novice guide, tell you all you need to know.