The first thing is to identify that the engine in your grain truck is indeed a 216. There is a chance that it could be a 235. That shouldn't matter, they are physically the same size engine, the displacement is different. If it is mounted in your grain truck there should be no difference in mounting in your 3100 using your bell housing/flywheel/clutch etc.
Use these
TECH TIPS to help you identify what you have.
TECH TIP #2 CASTING NUMBERS
