I reached out to the company that makes the product City Racer sells. Ironically my BJ45 is on their website for their product, but I digress. I too have 3 on the tree and the company, and I may wrong on exact dates, mentions 73+ so there may be a need to swap the steering column. This is appropriate in my case since I am dropping H55 in it. Outside of that I do feel it would be tough to use pre 73.Two things...
1st I love your firetruck....
2nd I havent read anything that suggests it wont work w 3 on a tree but I have no idea...
Again, love the firetruck