I have no clue if it's possible, but what about changing the tranny to the CRX HF tranny. Gear ratio is great!
88-91 CRX HF
1st 3.250
2nd 1.650
3rd 1.033
4th 0.823
5th 0.694
Final Drive 2.954 (3.250 in California)
^^^ Source
Just a suggestion, stay away from anything in CA. They have different emissions laws, and often things (trannys, etc), get built a bit differently. Resulting in worse mileage.