i need a 3.7 diff for the standard sunny houseing because i race speed way and i need to get the right revs for my cam at the moment im running the 3.9 and second gear with 185/80/r13 tires and it is reving to hard at 8 grand which is to much so any one got one or knows were i can get one its urgent

can any one help me i have a very highly modified sunny that i race in speedway and i need to get some softer shocks because the rear end ist to hard and i have stiffend the car up alot the only problem is that im not aloowed under the rules i race under i cant use ajustible shocks or konis if any one wants to see some pics off my car i will see if i can post them