This is what BK posted a while ago, and I am in the midst of doing right now:
http://www.rwgforum.net/topic/144657-making-a-gen-style-16710-case-out-of-a-16570-case-and-tw-bezel-assembly/#entry1089607
With a bezel assembly from any of the aftermarket, and crystal, you can use the movement that comes with the Explorer, get a nice dial and it should be an easy swap.
I am using the bezel assembly from Clark's, with crystal and insert. I intend on simply transplanting my dial and movement from my 'Retro'. The Retro case is not gen style crystal/bezel, and the lug holes are not drilled through all the way. In order to open those lug holes you need to use a split tip drill bit because the outside 1mm hole rarely lines up with the inside half-hole, and the bit 'walks' ruing the case. I ruined two cases before I made it work, and inside the lug looks like garbage. The 16570 case looks good, I am having lug holes drilled from it being blind, and if it survives all that engrave the correct numbers in between the lugs. I hope to have a nice 16710 rep when done.
But sometimes I think that 'smart' would be doing what By-Tor did and get a genuine one!