You have found the partnumbers for the case-halves. Most probably they are only there as an internal reference for Volkswagen AG as the case halves were only available as a married unit bearing a different partnumber than the ones you have found. The partnumbers are different because the parts are different, a left half and a right half. There is no way of knowing whether or not your motor is a 1776 by just these partnumbers. A custom built 1776 engine could very well be based upon an engine case bearing the numbers you have found.
I hope it helps,