swapping early 3.09 1st into later case

I searched but couldnt find a thread on this.

I have 3 833s ... 2 67-68s and 1 early Ball and trunion with a low 3.09 1st gear set.

Is it possible to swap the low gear set into the later trany ? And what does it entail ?

I want the low gear to mask the engines pulses at low speeds in 1st. Not to mention it cant hurt my 60ft .