alias mytest { tokenize 34 $1- | echo Result: $1 - $2 }

/mytest "file 1.txt" "file 2.txt"
Result: file 1.txt -

alternative method:
alias mytest { tokenize 34 $replace($1-, " ", ") | echo Result: $1 - $2 }

/mytest "file 1.txt" "file 2.txt"
Result: file 1.txt - file 2.txt