What are the differances between older diesel engines and newer models?

[Willys 741]

OK, My neighbor has asked me, what are the differences between the newer 451 and up diesel engines and the older 450 diesel engines...?
Why can't we fit the newer into the older? If not just the engine mated to the older transmission? He like some of us here love the benefits of the diesel engines over the gasoline versions and asked why not...?  I do not know the answer to give him technically speaking. All I think I know is they don't fit and have different computers etc.....but that's it. 
He has capabilities to get these engines from overseas if it is possible? 

So, does anyone know why it's impossible not to be able to do this?  In today's world of information and abilities it seems maybe it is possible?  OR is it simply size does matter and it's just too big....????   lol


Yes I know....just buy the model which has these engine already...?


Anyone....??????

[Mjolinor 85]

45o and 451 CDI have basically the same engine.

[Getfuzzy 18]

If i recall correctly the main difference was the fuel mapping, so it makes 54 or so hp.

[MikeT 737]

...and they have particle filters.....so the electronics won't be compatible.

[Willys 741]

OK, thanks....I have been looking at pictures etc of the differences between the years and the long blocks and their mounting locations for such things a water pump, air pump, etc etc and so far it looks as if the only possible option if one wants would be the 451. The castings seem to change after this model. Along with port sizes and shapes.

From what I can see it looks like you could swap in the 451 without much issue if you changed the intake,exhaust  and any sensor locations such as fuel rails or valve cover to allow you to use the 450 external engine/electrical systems..?  This is all simply by studying pictures and diagrams of the two different model year engines.  No actual physical conformations.  Does anyone have one of each of these model years to confirm any of these theories...?

All of this is simply to see if there is a bigger pool of engines we can choose from if the need arises?   OR are there any differences internally speaking making one better than the other?

[Mjolinor 85]

The 451 45 is almost the same as the 450. The 451 54 has more differences such as injectors (I think) and heaters. The 451 54 heater controller will not work with the 451 45 and vice versa. The 54 heater plugs are fast and if you use the controller off a 45 it just burns the heater plugs out and they are expensive. I have the T shirt on that one, it cost me £80 for a new set as opposed to £15 for a set for the 451 45 and 450.