Well, don't take my word, but I can think of 3 ways to achieve this. But all require some frame editing.
You can remove and re-weld your pedals where you want them to be. This will require you to change the chain.
Or... you could weld an extra tube for your seat to go in by welding an extra tube further back.
As an alternative, if you don't want to alter your frame's look, you can use a pipe bender to reshape your seats tube in the right way.
Imagine an "S" flipped 90degrees(CW or CCW). The one end on the right (facing down) will get into the seat socket while the one on the left (facing up) will be where the seat is.
Keep in mind that that's just me. There might be a way easier way!