Joe SVT brings up a good point...they way i found out that i had a spun bearing was it sounded like the motor was Metal on Metal and the car would not hold an idle.
Drain the oil,and check for Metal fillings...if you have any you most likly have bearing damage.
If any description on here is vague, let me know where you are, and maybe we can meet up so i can see whats up.
Any noticeably power loss?? CEL?? if you want to do a 3 liter swap, Low Budget is good at it, very good....but if you can't afford it, i would be willing to take up a few weekedns and help you, im sure we could get the block for cheap, and it would be easy to do...i ahve all the tools and all we would need is a garage...all you would need to do is pay for parts, and i can problably get you good pricing since i work for Autonation.
Let me know what you would like to do...first thing first, i would like the chance to properly Diagnose the vehical, if your local.
But at 4.5 quarts low on oil, I can almost gaurentee a spun bearing...I know thats not waht you want to hear, but im sure lowbudget and I could help you out iff needed.
Lupe