Inspired by curiosity and a topic on Manjaro forum I used @jonathon’s guide to create a similar guide - and revive a Manjaro32 
These are the rough notes - tested using a VirtualBox VM
Screenshot from final reboot
Mogrifying Manjaro32 18.0.4 to Archlinux32
Please note @jonathon’s comment below on using the 18.0.4 ISO from osdn.net/projects/manjaro32
Get a new mirrorlist
https://git.archlinux32.org/packages/plain/core/pacman-mirrorlist/mirrorlist
edit pacman.conf
- remove manjaro-system from HoldPkg line
- remove SyncFirst line (manjaro patch)
Follow instructions from Transition … section at
Accept package replacement/removal when required
sudo pacman -Syy archlinux32-keyring-transition
sudo pacman -S archlinux32-keyring
Remove conflicting packages
sudo pacman -Rdd pacman-mirrors manjaro-system manjaro-release bashrc-manjaro libxxf86misc menulibre
Install Arch pacman and pacman-contrib
sudo pacman -S pacman pacman-contrib
Remove
sudo pacman -Rns manjaro-settings-manager manjaro-settings-manager-notifier
Install - fix two conflicts
sudo pacman -Syu base linux linux-headers filesystem grub sudo systemd systemd-libs systemd-sysvcompat xorg-server xorg-server-common xorg-server-xwayland --overwrite --overwrite '/usr/include/crypt.h' --overwrite '/usr/lib/libcrypt.so'
build initramfs
sudo mkinitcpio -p linux
remove manjaro kernel (remove any dependencies - like drivers - remember to install opensource drivers if necessary)
sudo pacman -Rns linux414
update grub
sudo grub-mkconfig -o /boot/grub/grub.cfg
Reboot your system - don’t despair if grub shows Manjaro entry - it is Arch
Update
sudo pacman -Syu
You now have a Manjaro themed Archlinux32
