The number you give for the motor is wrong. The 116 part tell me it is a small V8 in the class 3.5, 3.8, or 4.2. Looking through the world parts system the lowest numbered 116 motor was the 116.960 which was a 380.
The proper motor for a 450 would start 117. Check what is stamped into the block behind the left cylinder head. Look between the firewall and the motor. The block sticks out and the number is stamped there. The full number will have 14 numbers grouped 117.986.12.xxxxxx. The 12 is for left hand drive (1) and automatic (2 a zero as in 10 would be a manual trans).
Do you have pressure gauges? Do you understand the principles that K-Jet operates? Do you understand how to change the mixture?
Bosch Master, ASE Master, L1
33 years MB technician