I recently got a machine with a 45 Loader.
Found that the Manual can be downloaded from Deere.
It includes instructions for assembly and installation on a machine.
The manual indicates the he loader kit includes the neutral rod PA318Guy posted about.
The relief was an extra - because the required one depended on 2wd/4wd.
This is from the manual:
IMPORTANT: Avoid damage! Use correct transaxle hydrostatic pressure relief valve.
• Two-Wheel Drive Machines: Use BM15043 (AM121248) which has “2WD” stamped on valve.
• Four-Wheel Drive Machines: Use BM15044 (AM122228) which has “4WD” stamped on valve.
As in PA318Guy's post, MIA885144 subs in for AM12228 - for 4wd tractors.
The parts shots are online, with the latest substitutions (so a better method than a printed parts book)
https://partscatalog.deere.com/jdrc/ parts catalogue link
45 loader is trickier than many models to find.
It's in a subsection (section 35) under '45 attachments'
I got a different part numbers
This part substitutes for AM121248
Part Number MIA884863
Description Valve Kit - VALVE KIT, VALVE KIT, RELIEF
Remarks(A) 2WD
and for 4wd
This part substitutes for AM122228
Part Number MIA884868
Description Pressure Relief Valve - PRESSURE RELIEF VALVE, RELIEF ASSY,
Remarks(B) 4WD