Voyager makes a very comprehensive PE set, to include sideskirts, but a good portion of mine went unused. The tie downs are nice as they have tiny spikes to help locate them. However, being flat, you'd still be better off using wire for a more realistic appearance. The stowage box latches are a little tedious as well. Still, it's worth the cost in my opinion.
Firestorm Models make a set of replacement wheels, but I'm still trying to figure out what's wrong the kit supplied tires.
There are also a few differeent mantlet covers out there, some in resin, some in a rubberish material. The resin one I have (Firestorm" Not sure...) was not very realistic on the upper left edge.
Best Value Models did a resin update for the '73 Sho't, which was very nice, but no longer necessary with the release of the new plastic kit.
Cromwell Models also do some nice conversions for backdating to a Mk I and a Mk II. There's a also a Mk III turret available in resin.