I have completed building a "109" in span Taylorcraft. I intend to fly it on floats. It has a 35 DLR swinging a 19 in prop. My question is do I need to add right thrust or was right thrust built into the kit? It is really hard to tell if there actually is right thrust, or down thrust for that matter. Would the plane behave errdically on take off? Should I just fly and see? Any help would be appreciated.

Set the prop at the horizontal position. Measure the distance at the prop tips to the rear of the aircraft center. That will tell you if it has any right thrust built in. Right thrust does help with takeoffs but nothing replaces the use of the rudder by the pilot.

Some thoughts.
Most kits have some right thrust built in, some more obvious than others. Not having it won't make it erratic but will require some more rudder during takeoff runs.

You said you intend to fly it on floats, I do a lot of float flying, I have 2 giant scale and a bunch of smaller float planes so I can speak with some experience. If you have the option to fly it off wheels first do yourself a favor and use that to get familiar with how the plane handles and get some run time on the engine if its new because you want the most reliability you can get.