Hi Greg,

according to Erich Groner's reference book, U177, built by Deschimag in Bremen, was a type IX D2.
Although some IXC plans exist, the only IX D2 plan I' m aware of can be found in Eberhard Rossler's book, Geschichte des deutschen Ubootbaus Band 1 ( on p. 198) where a general deck plan is shown. Unfortunately, it is a full size plan printed on ~ A4 format, which spans over 2 pages with a quality which would already be difficult for having it copied, if not scanned. The book's reference is ISBN 3-7637-5801-1 by Bernard & Graefe Verlag, Koblenz, 1986 (maybe later reprints do exist).
There is also a small booklet (A4 format, 68 pages) in the ' Vom original zum Modell' series, albeit on the IXC types, which shows also a number of detailed plans on deck apparatus (deck guns, conning tower guns, antenna, schnorkel). containing also a nuber of photographs).

Hope this if of some help,
best regards,
gH.