My first suggestion is for you to read my build thread. Or if you REALLY want details, read the LONG version on BangShift. I've done approximately the swap you're considering but in an S-10. My truck is ONLY used for LAnd Speed Racing so my swap is a bit more involved (in some ways) that a vehicle used for street use might need.

There are really NO electronics involved with an OM617. The stop system requires vacuum which you can generate several ways including the stock pump or you can do it with a simple pull cable. I had a specific need so I have a fairly involved system using compressed air - a safety requirement at the track.

I kept the Bosch alternator and starter (not much choice on the starter) but had both rebuilt at my local shop - so far so good.

The length of the engine will be the main issue. The mounts are dead simple - just a 90* thru bolt on each side. I set the engine angle and welded up part of the S-10 crossmember with part of the Mercedes trans crossmember to make the rear mount. Again, works OK so far. I had to modify my firewall quite a bit but I'm not sure on the Ranger. If you have a measurement from the firewall to the core support of a Ranger I can measure mine and give you a better idea of the available space. I'd run out and measure mine but it's still on the trailer from the last meet and it's raining cats and dogs at the moment.

You'll need to be realistic. You need a facility and metal fabrication tools (cutting, grinding, and welding equipment). To the best of my knowledge there is no kit for this so you'll have to make everything. Find out if the Ranger is set up for a front or rear sump oil pan - the 617 has it's deepest sump in the front and the S-10 has a rear sump so THAT was a stinker! I had to modify my lower oil pan extensively and will probably do another one to see if I can make more steering clearance. LOTS of cutting and fitting but maybe it's an easier fit in a Ranger.

The exhaust is pretty simple - just a pipe out of the engine bay. The first section of the Mercedes pipe will make the exhaust work easier.

Any radiator for a 5.0/Ranger swap should handle the cooling. Diesels are not generally hard to cool.

You should have a local driveshaft shop and they can connect whatever you have out of the trans to whatever you have into the diff. Jags That Run makes an adaptor plate from the M-B trans output flange to a Dana U-joint so that comes in handy if you go with a Mercedes trans.

Anyhow, it's a great project and I wish you luck if you decide to take it on.

Dan