It would be best to have a “parts car” to access for those things you miss.
In my opinion, it is easiest to have a V8 K-frame to start off with. Install engine and transmission onto the new K-frame. Rebuild the front suspension while there (if needed). Plan on dropping old engine, transmission, K-frame and suspension all at same time (with front of car raised up). Roll old “assembly” out, roll new assembly in, and lower car onto new powertrain.
This route, you can gather parts, rebuild what is needed to be rebuilt, etc., and perform the change easily in one weekend. Maybe even in one 8-hour day.
Now with that said – it sounds like you are going a different route – but there is nothing wrong with that. Depending on how you do it, it may take a full weekend for install (or longer).
IF you already have the Schumacher /6 to 318 mount kit (or a /6 to 360 mount kit - which is different), you already have a A904 (from your old /6) and have a A904/A998/A999 – then your old propeller shaft will be the same.
Parts you will need for change over (might not be a comprehensive list):
A 318 and automatic transmission. An A999 would be best transmission to use, if available. If you already have a transmission but not sure which one – there will be some numbers (transmission part number) stamped on it (as well as date of build and last part of VIN). Record those numbers (or take a picture) and post here. We can let you know what you have.
The /6 and 318 transmission cooler lines will be bent differently. A person might still be able to use them. This easier to do before engine install – than afterwards. Just make sure transmission cooler lines to not rub anything or each other!
The 318 and /6 radiator necks come out in different locations – so a radiator will be needed. They make two different size groupings of radiators: 26” and everything else (18”, 19”, 20” and 22”). The later 4 will interchange with each other providing /6 to /6 or 318 to 318 (but not vice versa).
Radiator hoses (which might be needed anyway).
Throttle cable. The /6 cable is longer – but is “too long” to be helpful. Note: there is a 318 2-bbl and 318 4-bbl throttle cable lengths, as well as a /6 1-bbl and /6 2-bbl lengths – or a total of 4 different throttle cable lengths available for FMJ’s.
Kickdown linkage. Note: Chrysler changed kickdown linkage designs almost every 2 to 3 years. They also have a 1-piece design and a 3-piece design. The 3-piece design uses 2 different bell cranks – which is the style you will need (3-piece design was used on all FMJ body’s and A-body’s). A few year other bodies used the 3-piece style but a majority used 1-piece designs. What year design you use doesn’t matter – just as long as it came from the same car. Also grab the intake bracket and transmission pivot bracket to have a complete set.
Note: it might be (will be?) simpler to just get a cable kickdown system.
Wiring harness is different. More specifically, the distributor pickup coil pigtail(s) are in different locations. A small wiring repair can correct that difference – just make sure you use solder and shrink wrap to seal the solder joints.
Both battery cables.
Heater hoses are different lengths and routed differently (minor issue). Sense you are now using new radiator hoses, it might be a great idea to change heater hose with new, at same time.
The alternator, A/C compressor (if applicable) and P/S pump (if applicable) can be reused – but all mounting brackets and P/S pump pulley will be different. Be sure to get a complete set of all pulleys, brackets and bolts for alternator, A/C and P/S. Or A.I.R. pump if required.
P/S hoses may or might not fit. There is a small chance they will fit, but don’t count on it.
A/C hoses will not fit.
Some A/C clutches are the same, but most are different (between /6 and 318)
Cooling fan blade, clutch and shroud.
Most 318 exhaust manifolds will fit – but not all will.
A /6 2-bbl air cleaner should work. A 1-bbl air cleaner will not fit (if using a 318 2-bbl). 360 2-bbl has a different size hole.
Performing a Lean Burn (or whatever name is on your computer) changeover – this would be a great time to do – if not beforehand. NOTE: this will add time (two hours, maybe) to the engine changeover.
Items that remain the same:
Transmission mount and crossmember.
The Steel fuel lines (already attached to body). The metal fuel lines on engine will be different.
Alternator
Starter – but this would be a great time to upgrade to a mini starter (optional).
BudW