Another big Mardave Meteor fan here too
Congratulations on your purchase... I too saw that on Ebay.US & though how strange that an example of the classic British buggy should end up on the other side of the pond, I guess its quite poetic that it should come into the possession of another ex-pat!
Regarding the rear wheels, the offset is such that the drive pin sits very close to the inside line of the wheel rim - I can't think of wheels from any other buggy with such a deep offset fitting. Of course you could machine up your own axles (which would need to be shouldered with a sleeve) - to allow for the alternative fitment of a wheel from a different buggy, but you would also need to machine in the drive cup to accept the end of the driveshaft. The dished red Meteor wheels are 2" - Schumacher still sell full spike & block tread tyres in 2" fitment which in the modern compounds work well on track - personally I'd try and find another Meteor wheel & run the Schumacher tyres.
Real early Meteor kits (with the three piece hole design wheels) it seems didn't come with a rear bumper - yours appears to be a mid-period car with the later 2" single piece wheels & corresponding tyres, but has the adjustable camber/steering links & bearing/bush rear hubs - which were also features of the older kits.... so in theory it should have had a rear bumper fitted... this was always a separate part to the main chassis on SWB cars - only the LWB chassis incorporated the rear bumper.
On the Meteor I've been racing this year, I trimmed one of the battery cups so that I could slide a rounded stick style LiPo battery in from one side, a pair of good strong rubber O'rings are wrapped around the end of the battery & the remaining element of the battery cup. I did make a plate that sits above the battery like the original mech-speedo plate, but I extended it so that it braces off the gearbox providing greater rigidity to the rear of the chassis.... but having a plate is not essential - there is plenty of room otherwise for the mounting of an ESC.
Penguin's reproduction of the SWB Lexan shell is period correct for your car - it was available as an option part from Mardave (its on the parts list I have from Jan 1988) - I also had a couple on my original Meteor BITD! That said I'm sure there's someone over here that is/was reproducing the kit style bodies in the original ABS material - it wasn't Kamtec, someone over on Tamiyaclub I think?
I've got a PDF scan of the instruction 'manual' - message me your e'mail address & i'll send over to you
....& here's my Meteor thread over on RC10Talk - which might give you some ideas
http://www.rc10talk.com/viewtopic.php?f=33&t=33237