Back to the original thread....
Original 6 was a 170, then grew up to a 200. Gearing with the 6 was 4.10 standard with 4.56 as an option.
The 250 is the same family as the 170 and 200, easy to swap in, but why?
The 240 and 300 are a differnt family.
For all you ford straight six needs, go here
http://www.fordsix.com
Since the 6 cylinder engine is longer then a V8 (just a bit narrower though) The transmission adaptor is shorter. There is a kit that uses the 6 cylinder adaptor, adds a block to bring it to the V8 length and allow you to cheaply bolt up a NP435 trans.
Do a search, there is a lot of info already on this board about swapping to a V8. Motor mounts need to be cut off the frame and replaced with V8, etc.
For the 4.0 V6. NO. It doesn't bolt up. You would have to transplant a bunch of eletronics, which is good if you were getting the power out of it. The only hope of a 4.0 is to swap engine/trans/transfer out of a soccermomobile. you would not be impressed by the results of all that work. I have one of those engines sitting in a ranger with a cracked head. Even that is getting a V8 for a replacement.
I think that gives the answers to the original thread.