Randy:
There is a lot of excellent reference material on the web about the Elco and Higgins boats. Probably the best website I've found is John Drain's site at:
www.pt-boat.com. He's in Australia. His web site is extremely detailed and a goldmine of info on building these boats at 1/20 and 1/35 scale. He also sells beautiful laser-cut semi-kits for both dimensions.
My boat is a 60 inch 1/14.6 scale of a British Vosper Motor Torpedo Boat. The actual boats were 73 feet long. I made the mistake of building to an odd scale so I ended up having to scratch-build everything on the boat. If you stick to 1/16 or 1/20 scale, you'll find supplies of guns, deck hardware and fittings on the web. I'd stay away from the white metal castings found on a certain site with a name relating to stinging flying insects. (If you catch my drift) That particular supplier's casting quality is very poor, for both white metal and resin parts. You'll spend a LOT of time trimming and cleaning up his work.
If you are into early Elco PT boats, you MUST see this web site:
http://www.geocities.com/patspt41/ Pat has built a near-museum quality model of an early Elco boat that is very impressive. His site also is filled with must-see info on PT boats and is well documented with excellent pictures and text.
If you intend to build a scale PT boat, you'll find these two web sites extremely helpful. Whatever you do, try to keep the weight down. Mine is 17 pounds, ready to run. A friend has the Dumas 48" PT 109 kit that he's 'modified' with lots of extra detailing including custom brass guns. His is heavier than mine and a bit of a dog. We both have the same running gear, 3, 18V Johnson drill motors, direct drive turning 3, 1.75" three-bladed props all powered by 3, 8.4v 3300mAh NiMH battery packs. These are big motors, about the size of a 900-series can motor. My boat scoots along just fine on the two outboard motors. I keep the center motor for my ticket back to the beach and 3-motor high-speed sprints around the pond. Each is independently controlled through a Proboat ESC.
Good luck with your build/modification of the Dumas kit.
Mike in Honolulu
http://homepage.mac.com/hookpilot/PersonalPage.html
to see my MTB in action