Ok Carfreak, here ya go....
The K-Member sits directly BELOW the engine. It is the main support that connects the right and left frame rails together. In small block V8 mopars the pickend of the oil pan is towards the rear of the engine just like a small block GM. In big block mopar V8's the pickup end , or the deep end of the oil pan, is in the front. So placing a big block mopar in a car that has a small block K-Member won't work. the pick up end will sit on TOP of the K-member instead of sitting around it. The enhine mounts wont line up, tranny won't bolt up, and you wont be able to close the engine hood.
I<....small block K-member
>I....Big block K-member
Concerning the engine situation. You are getting alot of info here and from your one post you sound a little confused. The info that you are getting is correct. Everyone is just giving you options. Cocerning switching a 440 over to a hemi.....don't waste your time. Racers did this when ma Mopar no longer made the Hemi. Go to your local Mopar dealership and buy a Mopar performance parts book. You can now buy the OLD style hemi that everyone so feared. The 440 is harder to get ahold of now a days. if you can find a old school bus, dump truck, moterhome with one it good luck. Just remember, these will more than likely have ALOT of miles on them. The 383's and the 400's will be easier to find. When you get the engine see if the tranny comes with it. You see Mopar did a switch on the trannys and engine combo's. If looking for a 4 speed, go for a A-833. Standard 4 speed on all big blocks. Put them onto 383's to hemi's. Just a different bolt pattern on the bell housing. the 727 tourque flight is a heavy duty auto tranny they put in EVERYTHING except cars with the 225 slant 6 engine. the 904 went with them. Some 904's went with small block V8's, but on the real light cars. ( Signet, valiant, early Darts) Anyway, GET THE ENGINE TRANNY COMBO. This is why....some engines were INTERNALLY balanced and some were EXTERNALLY balanced. It all depended on the tranny that was installed at the factory.
Concerning the rearend. When you have a car thats puts out marginal HP, then the stock rearend is fine. But going from a small block to a Big block. There is more tourque and Hp on the rearend. Pull a rearend out of a big block car if possible. Good doners also would be trucks with V8's in them. They just have a steeper rearend gears and you might be running high RPM's at 65 mph. But great off the line tho! In my Charger and my Road Runner, I ran 3:73's. Gave me a little shot off the line and good cruizing speeds as well.
The front end suspension used torsion bars. mopar used these to control ride height on the vehicals along with shocks instaed of springs and shocks that GM and Ford used. they worked VERY well. They came in two sizes as well. Smaller size for 225ci to 360ci. Larger size for cars with 383's to 440's. The hemi used the same as 440's with beefer threads and stronger bolts. They are bars that run along the inside of the frame rails and connect to the K-member abd a mid point support bracket under the front seat area. By turning them one way or another you can lower or raise the front end of your Mopar. In doing this you change the ride of it. If you do this or replace them you WILL need a front end alignment. EVERY TIME!!
I hope this answered some questions for you. Now their will be some people here giving their 2 cents worth and that is another point of view. i am sure there may be some things I ommitted.
Remember....No such thing as a dumb question.
DCON