92 SE-R

I purchased a 1992 se-r a few months ago. The girl who had it before me didnt take care of it. (apprently it was her 1st car) anyways it spun a bearing when we went to replace the bearings we noticed a weild in the oil pan. About a week after that the motor started knocking real bad, so i bought a JDM sr20de from japanese motor imports inc. anyways we had that put in the sentra, as we moved the 2 motors we noticed a significant diffrence in the weight, the JDM was alot heavier. about a week ago i took it to Big-O to get an allignment, they told me they couldnt do it. They said that the front of the car had sank by 2-3 inches. Im thinking that i need to replace the springs and possably the strut. But i was wondering if anyone had encountered this and if replacing those parts is the solution, or is there something else i need todo, because it is eatting away at the inside of my tires. Any advice would be useful.