Using an IncludeText field as Jay susggest is not the same as Insert Text from File
Jay's suggestion was to use an IncludeText Field, which while it has the same description of "Insert text from file"

is not the same as what I think that you are doing which is to use Insert>Object>Text from File.

As Jay suggested, if all of the files are in a folder by themselves, a macro such as the following will insert all on the required INCLUDETEXT fields, then update those fields so that each one displays the text of the assocatiated document, and optionally
unlinks the fields so that the results are converted to ordinary text.
Dim FD as FileDialog
Dim strFolder as String
Dim strFile as String
Dim rng as Range
Set FD = Application.FileDialog(msoFileDialogFolderPicker)
With FD
.Title = "Select the folder that contains the documents."
If .Show = -1 Then
strFolder = .SelectedItems(1) & ""
Else
MsgBox "You did not select a folder."
Exit Sub
End If
End With
strFile = Dir$(strFolder & "*.doc")
With ActiveDocument
While strFile <> ""
.Range.InsertAfter vbCr
Set rng = .Range
rng.Collapse wdcollapsend
.Fields.Add rng, wdFieldEmpty, "INCLUDETEXT " & Chr(34) & Replace(strFolder & strFile, "", "/") & Chr(34)
strFile = Dir$()
Wend
With .Range.Fields
.Update
.Unlink 'Optional to convert the result of the fields to text.
End With
End With
Note that with 755 files to process, it may take some time for this code to process all of the files and it is very likely that Word will display Not Responding.