There are a couple of sources for Excelsior/Enterprise B blueprints. The best ones are the Jackill Technical Readout Data Sheets which include all views and a cutaway corrected for correct deck height. I differ with him on whether those big modules sticking out of the back of the saucer are hangar decks or impulse packs (impulse actually), but they are still quite good.
The other set of blueprints is for a 'space control' ship labeled as USS Excelsior Ingram Class Plans executed by Star Station Aurora (PO Box 4990, Holyoke, Mass, 01041- but its an old address). These prints differ considerably from the screen Excelsior with extensive modification to the secondary hull. They are presented much like the Star Trek: The Motion Picture blueprints- in a vinyl pouch and lots of detail.
You should be able to find these products on the convention circuit (that's how I got mine), but maybe someone here can direct you to another source.
BTW, the Jackill series is very good and covers the majority of Star Trek ships from all eras, From Daedelus to Intrepid.
"The best diplomat I know is a fully activated phaser bank" -Montgomery Scott