changing engine from detroit to cat

I would find a salvage yard with Pete with a cat and get all the motor mounts an such also the trans will line in it the floor Pete has multiple diffrent fooled plates depending on shifter location

 

You will have to measure to be sure but the frames, on a blank are drilled the same for all modern engines if it is a big block, the mounts on the frame may be different, the hole in the cab should also be the same location on them. The Cat will weigh a little more, so the front axle weight will be higher. The front cross member on the older ones were different on different brands I do not believe that is the case now.
The CAC may be different, that you can check at a parts department.
You may need a different rubber elbow for the turbo inlet. The exhaust may need a different "S" pipe or just a different flange, depending on what the Detroit has.
Fuel lines just add extensions.
Battery cables should be OK, and the start circuit. Fan will need to be rewired. It is ECM controlled on the Detroit. You just need to wire in an on switch, and a fan stat.
The AC will need a different HP switch, hooked into the fan stat. Possibly the Low preasure switch also.
The throttle pedal, the cab will have to be modified to mount that.
That should be a simple re power. You will have to find the dash panels, that are compliant with manual gauges, speedometers and tack.
You may have to change the fan spacer to fit the shroud properly.

 

If I were you I would not try to rebuild that cat myself just by reading your questions It sounds like you would be in for a world of hurt. I have seen a lot of self rebuilds with big holes in the side of the block from a rod coming out thru them. Better to let some one with cat knowledge do the rebuild or stand at your side while you do it. Now I am not saying go to a cat garage but you sure better have a cat man working on it

 

Sounds like lots of work to me. If you are able to rebuild a Cat then I would think you should be able to pull your head on the Detroit and replace the most likely bad injector cups. As far as wireing goes too many people try and repair, splice, butt connect and scab together harnesses. Think of it as any other part. If its worn out and giving you lots of problems replace it. Or pull it out and completly rebuild the harnesses. When you put the harnesses back in take your time and loom and wrap everything and they'll last another million.