I'll be honest; I don't know that you'll save much by asking the builder not to do some of the cosmetic work - don't forget, he's getting his materials at Builder's prices (with discounts for bulk buying), plus he already has construction guys available, so what a contractor might quote to a consumer for a driveway (i.e. $4,000) would maybe cost a builder $800 (which is why a builder can offer "$20,000 of free upgrades" on a new construction house - it's only $20,000 retail, not $20,000 cost to him!) You might only get a credit that wouldn't equal what it would eventually cost you to do the same, so you'd be shooting yourself in the foot.
Also, ranches tend to be more expensive in general than 2-story houses, because the entire footprint of the house is on one level (more spread out on the land) and there are less of them - do you really want a ranch or do you prefer 2-story?
Exactly how firm is the price? Are you trying to negotiate on your own with the owner/builder? If so, you're getting shafted!! Get an agent - the cost of the commission to a Buyers agent is ALREADY factored into the commission paid to the Listing Agent of the house, the buyers doesn't pay any fees to a Buyers agent but the buyers agent is ONLY working for you, he negotiates on your behalf, finds out the exact price of comparable houses in the neighborhood and can bargain down the builder based on those, and will protect your interests throughout.
Often buyers think that if they don't use a Buyers agent, the price of that Buyers commission fee might help them negotiate a lower price on a house - in fact, not only is that NEVER the case (because as I said, in that case the Sellers agent pockets the entire commission instead), but in fact not having an agent may end up costing you money during the negotiations and could even hurt you in the process, since there's a lot more to buying a house than simply paying the builder the money!
If you really want to try and negotiate a lower price - WAIT!! First of all, they're under construction - they've been on the market during construction for 142 days without getting a contract yet - if they finish it without a contract, it will be sitting on the market during the winter months, at which point in time I'm prettty sure the price will start to become negotiable. You run the risk of losing the house - but if it does go under contract and sells, you know they have more lots available and so you'll know when the next one comes on the market to snap it up.
I would probably hold off....
Hope this helps. (Really, I would talk to a couple of agents and see if you can find a Buyers agent to help you!)