Hello. I'm sorry but I'm not Anglo-speaking, I use google translator. I know the answer too late, but if someone searches for this knowledge, it will be easier to find ...
55 spurs for a track length 253 5/8 inches 117.1 pitch (spurs distance) drive and idler wheel diameter 304mm (contrary to appearances, there are two diameters)
56 spurs for a track length 252 inches 114.3 pitch (distance of spurs measured from mounting holes) drive and idler wheel 298mm diameter. I hope someone will find it useful. Greetings Tomek