http://www.armorama.com/modules.php?op=modload&name=Sections&file=index&req=listarticles&secid=10
I did a pair of articles on the Italeri HMMWVs. You can find them both listed at the above link. Italeri did re-tool the chassis and included the proper 3-holed bumper in later issues of their kits. The actual body went through at least 2 additional toolings.
The second article covers some of the aftermarket items available to improve the Italeri based HMMWVs. Tamiya's original M242 Bushmaster armed HMMWV and both of Revell's HMMWVs were all Italeri-based HMMWV kits.