Defining a string and converting it to bytes at runtime is one thing, but I would want to have a constant array of bytes defined at design time and then pupulate it with a mix of bytes and strings.

HeaderArray: array [0 .. 123] of Byte = ($01, $08, $5B, $08, $0A, $00,
    $97, $35, $33, $32, $38, $30, $2C, $30, $3A, $97, $35, $33, $32, $38, $31)

How can I replace parts of the above with strings? (Say '5381' for the last four bytes).

Stuff like TEncoding.Default.GetBytes or BytesOf are runtime functions, aren't they?