What tractor are you working with? Yes it matters as some models require that the front gear case be set up to mount to.
It's very unlikely that a D1803 will fit in a D1402 setup.
I'll have to do more research when I get home.
You need to make sure the mounting points are the same, the bell housing bolts are the same, the pan bolts are the same and alternator location is the same.
Pan is very critical if it's a 4wd as the Drive shaft runs through or just under the pan.
If it as I suspect a industrial engine, you need to make sure it's not a fixed RPM engine or it won't work.
Also note that is a turbo motor and will require other considerations to make it fit and function.
