I would recommend that donor and recipient be side-by-side for the swap, so you can make sure you don't leave anything on the donor that you need for the installation.

I do believe that you'll need to swap over the intake or exhaust manifolds or both. I would try to keep the entire glow plug system from the 123. No idea how the throttle linkages will work.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC