I want to grab the last two numbers (one int, one float; followed by optional whitespace) and print only them.
Example:
foo bar bla 1 2 3
Match the whole line, so add a .* at the beginning of your regex. This causes the entire line to be replaced with the contents of the group
.*
echo "foo bar bla 1 2 3.4" | sed -n 's/.*\([0-9][0-9]*[\ \t][0-9.]*[ \t]*$\)/\1/p' 2 3.4