This probably isn't very helpful, but Two Hour Wargames used to have some prehistoric rules, though they don't seem to be available any more. They covered pretty much all you are asking for: terrain generators, small numbers, resources, character progression, etc., with the added bonus of being great for solo play. You might contact Ed to see if he has spare copies lying around (or maybe he's working on a new edition?). If you're really intrigued I have a mint copy I could let you have for a pittance.