I think in order to get your friend's engine into your car, you'll need to meet 1 criteria which is a letter which confirms your friend's car decommission. Meaning a letter saying his car will NEVER see the road again.
Normally people take half cut because the half cut is already certified with the custom form that say it's a junk metal (will not be use on street as a whole). That's why also JPJ inspection strictly check for any possible welding of half cut. It's part of the system to ensure traceability.
I hope you get what i mean. Next thing you need 2 know is where to obtain the 'decommision letter' i mentioned. I dunno which is the relevant department.