Is Upgrading CPU & GPU by Swapping Logic Board Possible?

Hello all,

I have base model 2013 iMac 27” (i5-4570 3.2Ghz / GTX 755M 1GB) and have been wanting to swap out the logic board with that of a higher end model iMac that contains the GTX 780M 4GB as well as pop in an i7 CPU.

I am fully aware of the complexity and cost of this job, as I have completely disassembled my iMac before to add a blade SSD and have been monitoring the prices. I am mainly doing this as a personal tinkering project.

Before I go any further,

1) Can anybody please confirm that this is a feasible job?

I am asking this because I am not sure if there is a different power supply between my base model and that of the higher end models containing the i7 and GTX 780M or if there is some sort of software block that will block a modification of this type.

I have found the correct GTX 780M logic board at a reasonable price and would like to pull the trigger. (NOT containing CPU)

2) Would I be able to pop in any i7-4771 or is there a specific Apple variant that I need to be aware of?

3) If I do not buy the i7 immediately, will my i5 work for the time being? (I am under the impression that both logic boards have the same LGA1150 socket)

I hope I have laid this out in an easily understandable format.

Thank you very much,

Julian