On the Dodge, it's a leaf sprung solid axle front end. Some guys clip the front frame and graft the front from an '80's Ram in its place to get the independent front and set a low ride height.
The 400 block is a B-motor. Same stroke as a 383, larger bore. The 440 is an RB-motor. Raised deck height over the B. The 400 has a larger bore than the 440.
The 400 block is a common choice for stroker kits. Used to be the blocks were cheap because nobody wanted them. All low compression smog era stuff. Guys would look for the higher compression 383's or 440's to play with. But the big bore and short deck height make a nice starting point for a stroker. A 440 crank with the mains cut down to fit a 400 block gets you a 451 that looks like a 383 and fits well in the A-bodies. Aftermarket long arm cranks gets you into the 496-505 territory.
None of that really helps in a $2013 Challenge budget. Especially since you bought the International. 
In reply to Rob_Mopar:
Thanks for the info. I do know where a running 400 and 727 is for $150. On the shelf in the shop I have a couple of freebee Dana 60's and a Indy tunnel ram (single carb) and I never ran the part number to see what it goes on. Looks like # 400-15 for a low deck? B?. So, I could be partway there.
I know of a truck V10 and transmission for $500. It is no Viper motor, but could be interesting.
I have not given up on the Dodge. They are cheap enough to get them both. I really like that wide flat bulldog face of it and and Express theme. I will pester the owner in a day or two.
Thanks again Rob.
T
Build the Dodge to haul the International. 
Compression on that 400 is going to be low. Advertised is 8.2. Reality is probably 7.8. That low and a tunnel ram usually don't mix very well. Forced induction is another story...
The 400/727 is a bolt in on the Dodge.
The truck V10 would be cool, but don't know if its worth the hassle. Lots of low end grunt. Not much beyond that. As a tow vehicle, that would be pretty cool.
