What kind of a problem am I looking at?
I have a 93 F350 DRW 7.3 E40D that is rusting out faster than I can fix it.
I am getting a 87 F350 DRW 6.9 ZF5 with a seized engine.
I want to put my 7.3 in the 87 and keep the ZF5.
Also putting my 93 front clip on the 87.
so what do I need to change to get this to work for the engine swap?

Sounds like a great idea to me.
Judging from the pictures you've gotten a fine machine there to build on.
Ok so engine swap is pretty straight forward they swap across no problem.
ONE SUGGESTION I HAVE AS A PREVENTATIVE ISSUE.....REBUILD THE OIL COOLER ON YOUR ENGINE PRIOR TO INSTALLATION.
Now it's a matter of retaining what you want and dumping what you don't want...
Eg...keep Serpentine belts...or swap to V...your choice! I prefer the serpentine setup myself. That's all personal choice type stuff...
Now as for the front clip...its about 12 bolts to physically to remove that whole clip...
remove hood and cowl and hood hinges IIRC
Two on top edge each fender on about 1/2 way down accessed between door and fender and one under lower edge of fender near forward edge of door, one in fender well holds inner fender in place and the two rad support bolts...that's it...two people can remove this quite easy...you can even leave the rad in if you so choose...I'd suggest unbolting shroud prior to removal of clip..this allows you to have wiggle room...dont forget trans cooler lines and of course rad hoses...

along with all the wiring.
You will have to contend with a different wiring for the OBS clip on the Brick nose truck...that's a bit of a problem but nothing significant what so ever.
I Did this clip swap myself on a gasser...was really easy...
Good luck and ask away if you have any questions...someones going to answer!
Al