If you guys do the group build and if you build either an 80' ELCO or a VOSPER, you might find John Lambert and my Allied Coastal Forces of WWII, volume 2 useful. It contains hundreds of drawings, including:
o general arrangement drawings for all types of Vospers
o general arrangements for PT 103, 109, 174, 562, & 596, plus the 70' & 77' boats
o weapons drawings for both Vosper and ELCO
o lots of isolated details like the Packards, radar masts, camouflage schemes, etc.
While it has been reprinted, your best bet would probably be to get a copy through interlibrary loan.
Al Ross