You can't cut that plate because it is the support for the bottom of the column. You really don't want to see what happens with just the two bolts holding it to the bottom of the dash.
Columns are not specific for 4 speeds or 3 speed autos, they will all work, you just need to find the correct years for your vehicle. Any of the later model ones will work, if they are from the old body style, but cutting that plate is a very bad idea.