18 inch wheels on 72 super?

[721302]

i have a set of 18 inch tsw trophys with 225/40/18 tires on them that i would like to fit to my super. The back of the wheel says et40 on them but i am not sure what this means. I really want Top Lines maxx struts but till they are in the budget i am going to use a set of 98 civic coils. My car is lowered about 2.5 inches by moving the spring perches down also. i hope it is not to low for 18 inch wheels. If any body has an info on the set up that i am going to try please let me know. Also going to have my drums redrilled for the 5x100 pattern for the wheels