the ls seems like a good buy, stock the 99 ls is worth probably around 9-10k or so, and the motor itself he probably shelled out around $4000-5000 depending on the year and mileage on motor
but i would personally get the usdm R, the stock suspension on the R is great, u will definitely feel a difference in handling between the R and the LS
and 5 lug conversion is always a plus (wider wheel selection)