You can find 4.10 rears in 7.5" and 8.8" - look for the Limited Slip version.
There are good gains with gearing. Great place to start.
Folks can talk all they want about Injectors, but when you actually do the math, you realize that the 14lb injectors are poop.
(112HP x 0.55BSFC on Gasoline) / (4 Cyl x 0.80 Injector Duty Cycle) = 19.25 lb/hr #BecauseMath
#FunWithMath: Step it up to 100% Duty Cycle! (Warning! Possible Engine Damage!)
(112HP x 0.55BSFC on Gasoline) / (4 Cyl at 100% Injector Duty Cycle) = 15.4 lb/hr, again #BecauseMath
My 1989 Mustang 2.3L puts 70.1HP to the ground and is MAXED OUT on the 14lb fuel injectors, in 2nd gear and started to run out of fuel at 5K RPMs.
[Edit: I have lower fuel pressure and a return style system]
Now, injectors will NOT add HP, but they directly support HP. If you do anything more than exhaust or intake, you already NEED injectors.
Set up to 4 hole injectors, the idle quality is awesome.
View attachment 44928
I went to 36# 2019 Mustang FFV Injectors and USCAR Connectors - but this requires a tune.
Even "Way Over Injectored" in stock form, the idle quality is SO much better than stock.
The thing to remember is 90+% of the HP potential of this platform is in the cylinder head.
You will need to make the vast majority of your mods there.