1963 Valiant differential rebuild kit and ring and pinion gears

That would be awesome. Thank You! Honestly, anything less aggressive than 4.1 would be welcome. That would really compromise the car's top speed too much I fear. Any insight into what is different with the carrier gear kit between a 1963 and what is available on the net today would also be awesome... is it the number of splines on the axle's or what?

Thanks!