[Proj] towgs84 functionality

[Jeff Huber]

I'm new to this, so here is a, hopefully, simple question.
Why don't I get a shift when I use towgs84 in the following:

invproj +proj=utm +ellps=krass +x_0=500000 +y_0=0 +lat_0=0 +lon_0=75 
+k=.9996
701176.9 7550769.7
79d48'58.181"E  67d59'57.701"N

Expected to get +79.8161616,     +67.9993614  so that one is OK

invproj +proj=tmerc +ellps=krass +towgs84=28,-130,-95 +x_0=500000 +y_0=0 
+lat_0=0 +lon_0=75 +k=.9996
701176.9 7550769.7
79d48'58.181"E  67d59'57.701"N

Expected to get +79.8149530,     +68.0000817  but did I get same answer 
as above

Am I using towgs84 incorrectly ?
Jeff