Hi,
If I understand you correct, you should be able to make this from the admin.
Placing manual orders through admin, then "conversion pixel" should not be activated (if it is placed on the success page) ?
Process would be something like:
1) Go to Sales > Orders > Create new order > Find existing customer / Create new customer
2) Then fill out the product / order details.
3) Fill out Shipment provider
4) For payment - choose your provider (be sure the can handle this kind of back-order-payment)
and you should be done :0)
-- Best regards --
Kent Christiansen | Magento Certified Solution Specialist