Hi Jim, Yes it can be done. Creative car craft (i think thats the name) sells a fiberglass tin kit that will fit around the T1 engine and adapt it to the T4 engine bay. I did the engine swap a few months ago but had original Euro tin for mine. The Bus came with a T! engine in europe as well as T4.
You will also need to build a custom engine hanger for it. If you want to use a T1 baywindow air filter like I did then you will need to weld in the air cleaner mount on the right hand side. Also keep in mind you will need to use a 1971 DP intake from a bus or weld on a fitting so you can attach your vacume hose for the booster. You will also need to swap to a longer 68-71 acc cable as well as a few small wiring changes to work with the alt/gen combo on a T1 style engine.
Hope this helps.