We've done this conversion several times over the years. Not too difficult - you just need a jig and surface table to work off of. We've done flat karts and champs with good success.
I even sell the parts if this is something you want to tackle on your own.
have done it just build a gig and cut off the old and weld on the new its not hard i got everything from bmi karts worked great cost about 125. when i did it
Strong consideration should be given to the location of the king pins. Putting on the heim joints will most likely widen the front track. Try to set up the new installation to maintain the original karts track between king pins and from the centerline of the kart. It will effect chassis setup and handling if it moves out wider.