I did a post with pictures on the conversion that I did a while back in the DYI forum. The one-handled faucet that I found required a large circular hole but the diameter was just about the same measurement as the distance across the two holes for the original faucet, so the new faucet fit in the same place as the old with no problem. The only addition was the hole for the hose fitting which I put a couple of inches above the new faucet. I used shark bite fittings which made doing the plumbing easy. Maybe the 90 deg elbow type would work in the space you have.
Miles