Alphabet Position Finder Inspired by the Codewars Kata.

Your goal is to take an input string such as this one:

"'Twas a dark and stormy night..."


and return a string containing the position of each character in the alphabet, separated by spaces and ignoring non-alphabetical characters, like this:

"20 23 1 19 1 4 1 18 11 1 14 4 19 20 15 18 13 25 14 9 7 8 20"


For an additional challenge, you can replace any numerical characters in the original string with themselves + 27. For example, "25" would become "29, 32". This is completely optional.

You must use 1-indexing ('a'==1, 'b'==2, etc)

Additional rules:


You must return a string, not an array.
Trailing whitespace is OK.


The winner has the lowest byte count. 

Good luck!
05AB1E, (5?) 7 bytes
Rightmost two bytes are output formatting
áÇ32%ðý

A port of my Jelly answer, but O5AB1E is more terse for the alphabet filtering.
Try it online!
How?
áÇ32%ðý - take input implicitly
á       - filter keep alphabetical characters
 Ç      - to ordinals
  32    - thirty-two
    %   - modulo (vectorises)
     ð  - push a space character
      ý - join