Automobile(s): '80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
Re: 368 8-6-4 Woes.
The engine drops in but it won't be driven anywhere without some extra work. 425 into '81 car assuming rear wheel drive.
Oil pump housing swap.
You have to figure which air conditioning compressor to use. I like the old axial. You can then get the AC hoses from compressor to expansion tube and compressor to accumulator tank. This way you keep all the 425 brackets and stuff.
Pull out the check engine lamp and leave the DEFI compuker in place to run the AC.
The fuel pump in tank can be regulated down to carbonator pressure levels with a hot rod type adjustable regulator but a bleedoff loop back to the tank helps cut down vapor lock issues. Another way is to pull out the stock sender and dump an earlier one into the tank. You will still have to fabricate some fuel line up front.
Carbonator linkage is slightly different but can be overcome with a little fabrication. If you want the electric downshift then fused 12 volts must be found for the switch on the side of the rottenchester.
Exhaust is similar but 368 pipe sizes are smaller than 425. Choices here depend on what you want and what you have on hand.
There are a few more small things like properly losing all those extra underhood wires which now do nothing.
If you want to go Edelbrock, you will have to use the A/C compressor from the 368 and the thermostat housing. Granted, I've only helped do this swap once, it was simple enough that I remember thinking that I could have done it in my own garage.