See if this helps. Timing of your question is great as I have my 2004 T-1950 all apart and can take pics of how it is built.
This is a side view. I have the small grab handle on the 1950. I have the large grab handle on the T-310SR like you linked. I have included this just so you can see what a 2004 vintage 1950 has.
Here are the wall studs on the door strike plate side.
The door stud on the strike plate side is made up of a nominal 1" ish x 2 ripped stud. The actual is 15/16" combined from a 3/4" ripped width stud combined with a nominal 1/8" luan shim by 1 1/2" longer dimension which is the wall depth. They must rip these from 2 x something stock. And the 1/8" luan is no longer a real 1/8" it is a approx 1/32" less.
Sandwiched right next to it is a nominal 2 x 3 stud turned to lay flat the 3" direction. This actual dimensions are, 2 1/2" x 1 1/2"
The combined width is 3 3/8" actual, total.
Yours should be the same or very similar. Feel for the hard support in this area to lag the larger grab handle to. Note: They have a 1/8" siding shim that you can see on the full width direction. This shim helps correct for siding warping. The full 3 3/8" width does not have this 1/8" shim, only about 1" of it where the door frame screws through the siding.
My T310SR has the grab handle flush with the edge of the door frame molding in the left to right direction.
Hope this helps
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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