An FD RX7 does not have a great deal of room to work with. You going to be limited by the amount of space you have to work for batts. expect maxx 60-80 miles wit the space you have to work with. unless you want to use 6500 AA batts with. Costs can be from min. $6k-$35k all depends what you want to spend on batts and how many you can fit. check out this one here done with lead acid but a great motor http://www.evalbum.com/260.html