Export Fixed Width Table with 2 Different Lines

[vbreezy]

I have a table that has two parts to it:

The first record is the "Order Header" and has certain information in it, with specific field lengths.

The second record is the "Order Line" and also has certain information in it (some of the fields and field lengths are different from the first record).

I need to combine these two records (Order Header and Order Line) into one table and export to a fixed-width .txt file

Here's a sample Order Header field specs:
char(3)
char(10)
char(20)
char(10)
char(4)
char(20)

Here's the sample Order Lines field specs:
char(3)
char(10)
char(20)
char(20)
char(20)
char(20)

As you can see the first three field and the last field match lengths, but the two in between don't. Does anyone know a way to combine this information and have both records show correct field widths when exported into the .txt files?