...before you have to wait/travel to procure replacement end cap gaskets, you can easily make your own using rubber gasket stock from NAPA. Be certain to check the end caps for flatness. Lay each one on a flat surface and check for true. 'Nurse' any deformations out with gentle hammer taps.
Nope,
Got a 4" heatexchanger. Finally got to where I could measure it. The whole engine is kinda tough to get to and work on when it is setting down inside the center poontoon tube.