I know this has been talked about, so i did some research.
After my research, i started buying parts.
Here are the parts you need:
51380-HP7-A00, left front upper control arm
51370-HP7-A00, right front upper control arm
51350-HP5-600, right front lower control arm
51360-HP5-600, left front lower control arm
44615-HP5-600, front drive hubs (need 2)
53521-HP5-600, tie rods (need 2, this is just the adjuster rod, not the tie-rod ends)
51200-HP5-600, right steering knuckle
51250-HP5-600, left steering knuckle
53235-HP5-600, steering arm (connects the tie rod ends to the steering shaft)
23611-HP5-600, "final shaft", goes inside the engine, provides power to front and rear driveshafts)
40400-HP5-600, front driveshaft
44250-HP7-A31, right front axle
44350-HP7-A31, left front axle
11300-HP5-000, front crankcase cover
50350-HP5-600, front differential support bracket
41400-HP5-A50, front differential unit
You also need the 4wd shift lever and the cable that connects it to the differential. there is not a part number for the whole assembly, just look on ebay. thats where i got mine.
Now on to the good part, the turning of wrenches:
Here is the engine before removal:
front differential in position:
^^^notice the "TRX420TM" decal, indicating 2wd
Here is a pic of the "final shaft", comparing the 2wd (in my hand) to the 4wd (in the engine).
^This is the most difficult part of this conversion, removing and opening the engine to swap out this shaft. However, there is a lovely video on youtube showing how to rebuild this engine and they clearly show the steps to remove/replace the rear cover and final shaft. Dont forget to remove the front cover before installing the new shaft, it will not fit thru the 2wd front cover.
link to video>:
once the new shaft is installed:
you will need to install the front and rear covers using sealant, make sure all shims/washers and o-rings are in place in the correct locations referencing the video above.
here is the right front corner mostly assembled:
and fully assembled with hub, rotor, and brake caliper:
I do have more pictures to upload, when i have more time i will update this further