Sorry about your vent.
The wood, I'm not aware of any special wood like in cedar, pressure treated etc. . Sunline did use a lot of light weight wood but is was more truly for weight. If what ever wood gets wet it is not great. If you have access to a table or radial arm saw or even hand circular saw you can rip and or recreate the shape as needed from pine, Douglas fir etc. A home Depot/Lowes run.
The biggest thing is while you have the wet piece out, look good and long for any other wet anything, like insulation. Once you seal it up good, any wet that is hiding may not be able to get out until it rots out.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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