I can't get my column to shift into park or low - what am I doing wrong?

The length of the pivots must be the same on the transmission as the steering column  (the column is 2 7/8 and the transmission linkage should be the same).  When you set up your linkage start with the column and transmission in neutral.  This will give you a central location to start from, allowing you to split any variation in the low gear and park detents.