you need a street clutch and a 2.88 T-10 or a 2.98 Muncie-style 4spd If you want to drive this on the street. If that is a road race jerico, the 1st gear is only a pit gear anyway, all your racing is done in 2,3,4. With that axle ratio they're probably in the 150mph range on longer courses in this car.
We support the SCCA A-Sedan series with a spec gearbox. There are Jerico's, TKO's ST-10s, our Muncie-esque 4spd and a couple guys running T-5s.
For racing you'll see guys with 3.08s, 3.23s rears and 2.56 or 2.20 1st gears in the 4speeds . But, its not street friendly for most people.
If this is a street application; either go to a 2.88 T10, 2.98 'Muncie' or a 5spd like a TKO and never use the overdrive since you have 3.08s.
The other option is to jack the axle ratio up to suit the gearbox better. Probably something like a 3.73:1.
Start at the beginning; find out which ratio Jerico you inherited and then we can advise on a clutch/trans or axle combo to suit your budget and needs