Good point here about the safety aspect with the steering column. If the car doesn't already have them, get proper 3 point seat belts in there. This should be high on the ol' priorities list.My 65 was a converted from a six cylinder as well. One of the first things I had to do was upgrade the steering linkage to the heavier duty V8 items. Something to check. I don't know how to describe the six cylinder component's but when you compare them to their V8 cousins they look spindly as heck.
Good luck with the car. Make sure your son understands these cars are not to be taken lightly. There is a 5 ft. steel shaft pointing at your chest so following distance is crucial. Lots of threads on that here on the forum so we don't need to go onto that but I suggest you read them...