Model 4 1050

can you increase the gross weight of a mdl. 4 1050 to 1200 like the classic ? and is the interiors withe the same ? I am 225 lbs and 6' 2" trying to find the right plane.

The differences in gross from a model 4-1050 and a 4-1200 are in the strength of the strut carry through fuselage tubing and the strength of the struts as I recall. Obvious visual difference between the two is the vertical stabilizer and rudder. The 4-1200 is taller by 10" and a couple inches deeper.
A model 4-1050 tail is the same size as a model 3 tail.

The mods to beef up the 4-1050 require drilling the centers out of the strut carry through ends and inserting a steel rod from one end of the carry through to the other and welding it in properly too carry the extra loads. Then you have to replace the 4-1050 struts with 4-1200 struts and rod end bearings. The strut tubing is larger in diameter and may be heavier walled also. The welding may require recover/re-paint of a part or all of the fuselage. Kind of a pain but a few have done it. The strut replacement is straight forward and simple but probably not inexpensive. Personally I wouldn't go through all the fuss and expense. The few 4-1050's that were made seem to find happy homes fairly easily without going through the modifications.
Much simpler to hold out for a model 4-1200 or a Model 4-Classic(not many of those around). The cabin sizes should be the same on the 4-1050 and the 4-1200. Sit in a model 4 (either one) and test it for size. You may find a model 5 ,6 or 7 fits you better but try the 4's first. Best of luck. Do a little homework on the model differences. It's worth it. Gives you a good base knowledge of the lineage of the design.

Another difference between the 1050 and 1200 model IV's is the counter balance weights on the flapperons, 1 each on the 1050 and 2 each on the 1200. This also leads to a higher VNE, 125 for the 1050 and 140 for the 1200.