Hijet 1.3 engine issues/swap


Hi all,
I know there are a few discussions on here about engine swaps for the Hijet but I was wondering if anybody with any experience of doing this could help me?

I have an X-reg Hijet van with the 1.3 EFI engine but it has succumbed to the overheating issues that these vehicles are known for.
I had it running for a while and it was great, but the head gasket has definitely gone and oil pressure issues amongst other things make me think that a replacement engine is my best bet.
The van itself is in great condition and I want it up and running again, but I was thinking about a full engine replacement/modification to make it more reliable and better to drive.

I am quite happy to carry out modification work to the van itself if required as it isn't used for a particular purpose and is a spare vehicle. I can cope without it for a while if needed.

Also I have a range of spare vehicles sitting around with functioning engines so quite happy to take all the necessary bits from one of those if it would work?

One of the potential donor vehicles I have is a Daihatsu Copen with the 1.3 engine. Not sure if that would fit under the seats of the Hijet. But does anybody think it is possible to do this with a bit of modification? Or is it completely the wrong type of engine?

Also, would mounting an engine at the rear of the vehicle work? Would it be possible to drive the rear axle directly from an engine situated at that location rather than install is at the current location?
Or are there too many factors that would make this a bad idea?

Any help is appreciated.