Piece of cake.  If your 1936 cabs are 8 ohms or 16 ohms, then were good to go.  I HIGHLY recommend using one cab left & one cab right.  The following explains stereo options as well as mono.

Typically Marshall cabs that are stereo have FOUR ohm options two for Stereo, two for mono.  If you use one cab for left and one for right, then each cab input must be set to MONO and plug into the 16 ohm side of the input plate.  If you are using both cabs in stereo, then plug each side with the 8 ohm input jack on the plate while switched to stereo mode.  You will also need to SPLIT each out put as you will have two LEFT and two RIGHT to plug into with both cabs in stereo mode.  No big deal to do, just need a speaker cable that is a "Y" cord.  you CANNOT daisy chain from cab input and use the other input as an output.  The stereo cabs are not designed to work that way.

Simply hook them up to the external speaker outs that correspond to the outputs to you want each cab to be.

You MUST then PHYSICALLY DISCONNECT the internal speakers from the Vetta. 

It's best to pull both clips off each speaker, then wrap them up with electrical tape SEPARATELY so they do not touch anything or worse case - each other.

If you will ALWAYS use external cabs, then you could make the Vetta lighter by removing the speakers entirely.  However, if you choose this option, you MUST NEVER use the combo without any speakers connected unless you TURN OFF the speaker outputs from within the output menu on the Vetta.  Using the head with the speakers on without any physical speakers connected will eventually burn out your head.

This should be your answer and if not, please write back and let me know more about your 1936 cabs if they don't match what I believe they should be.  Thanks.

Take care,

Neal