The rim tyre questions :)
If you have a stock mr2 sw20 my response is no.
Why...
Rim width equal tyre width. Rims width is designed for a tyre width, based on sidewall stance to give you the tyre strength. Base on your rear rim width 9.75 you would be looking at a 255-285. 245 is the widest rear (generally) for no scrubbing, based on correct offset rims. Therefore anything larger need rolling and other magic (flares) to try to remove the rubbing. Look up tyre width rim chart. However the width fit will also be impacted by offset.
Offset is the MR2 challenge. From memory the rims you are looking at don't come in the required offsets (mr2 sw20 et35ish 8" front and et40ish 9" rear for the mr2 sw20). Do a little google searching mr2 offset and will give you more info.
Back to tyres. Your looking at cheap rims, 18 x 9.75, best check the tyre prices. Ffor the sizes you are requiring, and to match the side wall rating required for a mr2, you could be up for some seriously expensive tyres for decent tyres.
Suspension will also be a deciding factor. Type of suspension will impact your offset and width. I changed suspension brand and then the rims rubbed.
18s on a mr2 (sw20). 215/35/18 (front) and 235/40/18 (rear) is what I have, they don't scrub but you need camber bolts and camber plates to get correct camber (rubbing only when lowered). After running 18s, the rims look big with rubber band low tyres, however recommend trying the ride comfort (or lack of) before buying.
P.S. I learnt the hard way and I am now selling a set of 18s (cheap), near new tyres. Going back to 17s to gain a little sidewall height and wider width, less harsh ride, hopefully won't kill the suspension like the 18s.