Rear end advice for racing with a 4 speed

I have the dump truck rear in my Duster (Strange S60). I like the strange over the OE as it has side adjusters instead of fighting shims. I’ve got 4.56 and my 4.30 gears set up on spools and with the shim packs for the pinions it really doesn’t take that long to swap. I also have 4.88 and 5.30s but not set up. To be honest…. If I were to do it today it’d be a 9” style. I say style because none of it would be factory ford. We started having issues with the 8.75 when we started running 10s. Got rid of it all and stopped the bleeding. I will say the S60 has been rock solid and my .02$ is that the op is going in the correct direction on upgrading.