Er, gosh, not sure I can remember back to V3 (probably never got to that stage with it as V4 came along quite soon after I got V3.
In later versions if you define the PAGE header template (Perhaps that is what you are using as a report header?) where the page header lines repeat become 'invisible' to Monarch as it processes detail records and other appends. So those lines don't count except as line to extract Page Header info from. So providing you allow for blank lines in the page header section the other template should see a continuous record.
I really don't recall if anything changed in the later versions and I don't have instant access to one that is old enough to give some clues from reading the 'What's New in the release' sections of the user guide or help file.
There can also be secondary issues to deal with if the reports are doing some clever things with not splitting record section blocks over a page - for example not splitting a text paragraph - which may need further consideration over and above Page Header question.
Hopefully someone else may be able to give a more precise answer.
Let us know how you get on.