2.54:1 1st gear is the M21 version used in V8 HK-HG applications and also on 6cyl HK passenger vehicles as a heavy duty option. The M22 version (2.85:1 1st) was standard on HK-HT commercials when a 4spd selected, also optional on HT GTS. If you have an M21 out of a commercial it'll be from a HK 307 or a HT-HG 253 or 308.