You could make 't better...
Put the suspension, wheels...etc., aside: they 're wrong ! Take the AFV M3A3 running gear, or the ol' Tamiya...
You need to round off the back of the upper hull; all M3A1 've a rounded back....Well, most of them ! Hull sides ' re wrong...Too hight ! You need to remove some plastic UNDER the rivet line ( +or- the thickness of the mudguards...See the boxtop illustration, it shows you how it must look like ! ). Of course, if you do that, you must work on the middle LOWER hull, because it 'll be too low...! That ' s life....Isn' t !
And the gun mantle 's the wrong shape....Try AFV again.
Btw, the AFV M3A3 's the best of the M3 kits family...Bad news: you ( the US ) didn' t use 't a lot, in WW2 !