Do you know the specs of the rubi wheels? Did a quick search and came up with 7.5" wide with 6.25" backspace. If that's the case, with your 1.25" wheel spacers you're basically running 7.5" wide wheels with 5" backspace... which means these wheels will stick out 1.5" further than your current setup.
Same as posted above, turn your tire to full lock and see if you have 1.5" of clearance (imagine the tire being pushed out another 1.5" perpendicular from the hub, into the firewall)