a few questions about a new to me 1990 Euro 3.1L

1) what can cause unusual noises to come from what seems to be the suspension on the rear when visually I cant see anything wrong?

2) the car has non-stock wheels and tires on it - they are size 16 inch - I have custom wheels and brand new 14 inch tires on the other lumina -what could happen and what can I also expect if I switch tires and wheels putting the 14 inch on the euro that currently has 16 inch non-lumina wheels and tires

3) which kind of antifreeze came in these standard? - green or red - I hope it wasnt dexcool stuff - if so, I may need help washing out the coolant areas and installing green

if you can answer any and/or all 3 of these questions, I am open for answers - once I swap from one car to the other the stuff I know I can swap, I am junking the 4 cylinder and it threw a rod and it just plain wore out everywhere except the tires and wheels

A 1991 should have been filled with silicated PEG coolant (the green stuff). You should still flush it thoroughly and replace it.

FWIW, I have been using DexCool in everything I have with no problems, including a 1986 Trans Am. I used to replace heater cores about every 3-4 years before switching, since the car sits for long periods with no use.

Installing all four wheel/tires should not cause any significant problems, so long as the backset is correct. If the overall diameter is close, the speedometer/odometer should not have significant error. What sizes are the tires? The car should have a label in the LF door jamb showing the proper OEM tire size.

The term "unusual noises" is pretty broad. Care to elaborate? Squeaking, clunking, rattling, what?

I will reply with exact tire sizes soon as I have both sizes

The noise is kinda like a rusty sqeak with some clunking when I enter the car and when I go over bumps at slow speeds - I hear it sometimes when I go around corners as well - I cant see anything visually wrong yet - are there bushings that might be gone due to their age I need to look for as well as other things? - if it is possible the strut shocks are wasted, can the struts from a plain lumina swap to the euro model do you think?

I appreciate the assistance you have given so far

The sounds are very similar to my 94 3.1 Euro Lumi. From what I have gathered the creaking has to do with the ends of the Leaf Springs being worn down, the rubber pads that are in contact with the spindles. I have yet to do anything about this myself other than spray some lubricant in the area. I believe the whole replacement is costly. As for the "clunky" noise, I have that as well, my rear struts are bad and will replace them soon. (I have the parts in my car) I am not convinced that is what is causing that sound though because I hear it more from the front. I do have a torn CV half shaft boot on the passenger side. Check both sides of your Lumi and see if you do too. I have read sway bar end bushings that are bad as well as tie rod ends can also produce clunky sounds going over little bumps and turns. I haven't had time to change mine yet to see though. Good Luck and enjoy the ride! I have always loved my Euro since I got it in 1999.

If you change the anti-freeze to the Dexcool you will have fewer problems with the cooling system as the "green stuff" has caused many problems with corrosion in the aluminum parts in the system. this is why Dexcool was developed.
The clunky sound is most likely struts as previously stated. However badly worn rear spring ends may also cause this noise as the recede from and advance toward the rub surface at the hubs on the rear. Check to if the spring ends are worn into the spring itself. If more than 1/4 worn into the spring, it is time to think about replacing them (very expensive), or build them up with JB weld and put 1/2" or 3/4" rubber pad on wear surface.