How about taking an old Hasegawa 1/72nd scale M3 Lee kit and kit bashing it together with the track units from an Armourfast Sherman kit, both to speed up construction and to make a more wargame proof model? I also just happened to have a Hasegawa kit in the loft, complete with a faded £3.75 Beatties price sticker to show you how long I've been collecting plastic kits!
Incidentally, I've now also modified the front mud guards as I realised that they weren't correct. I also left off the rear deck stowage bins, as Soviet M3's often had these removed for some reason. The cupola machine gun was also omitted as I thought it would be too fragile for gaming purposes, but I may replace the plastic part with a piece of brass rod or similar?