Hello,
I know the K-series engine swap is a common engine swap into the 323s, but all the information I can find regards other models of the 323 and not the BG specifically. I know the KF is usually the-go-to engine for this but how much harder would it be to swap a kl ? Some people claim that it's basically a drop-in plug-'n-play swap and the only thing you need to concern yourself about is the Intake manifold and other people claim that the chassis difference between the BG and BA is quite big and you need to consider a lot of other factors.
My main concern is wiring.
Thanks for any help.
( This is the engine I am considering putting in if anyone wants to check it out: https://www.car.gr/14742916 )

It has been done and is not hard. Sourcing the parts is usually the issue. My friend swapped a kl into his 323 bg saloon. You need a mx3 ideally as a good donor car for mounts and bits. We swapped the front subframe and rear over ( giving disc brakes). Also its much easier with an injection wiring loom in the 323. It's pretty much plug and play really