It can done, maybe not easily but 98 % can be bolt in, no welding ,fabrication if you plan it out and get all the right bits.Almost every day someone on the Samba has at east some of the parts to do it. I would do a bit of research before like the Samba forum and another good one from the UK is club 80-90. You will need engine mount carrier bars, motor mount brackets, motor mounts, bellhousing ,oil pan, oil pump, cooling hoses, etc. Those trucks came with diesels from the factory so everything should be available. I would suggest going the TDI route either full or mTDI , if you can find the right motor etc. The only fabrication issue may be the turbo /left engine mount problem and fitting an intercooler. Many people have done this so the info is out there.