I suspect the difference between them is length? Which is crucial for your setup...

Just found another NOS spindle which even though it came with a SV arm (handed) seems identical to the old OHV one. (the repro one is longer)

In the 33/34 parts book 335-30 is listed for side valves and 335-31 for overhead valves....

It will be the same spindle part but your rockerbox looks like this with the lifter on the side plate?

I've got a spare, unused, one from Drags and even though it is a bit 'clunkier' than an original, it will fit a '34 rocker box I think you have to thin down the lifter a bit

It has a certain lawnmower feel about it??

This is another system, one that is followed by the Czech reproductions.

The top pressure plate is pressed rather than turned.

One spring and grease does the job here.

This is another system, one that is followed by the Czech reproductions.

The top pressure plate is pressed rather than turned.

One spring and grease does the job here.

Here is an Amal dual lever taken apart just now - no cork just grease and lively spring washers

The 0724 bolt is for the '33 head and the 170-34 bolt is for the '34 head (with the smaller 14mm spark plug)
The problem is going to be how to mount your rocker box - the '33 box was part tinware whilst the '34 box was all cast.
The '35,'36 and '37 heads all lower the "stands"(?) for the head bolts ...

An original and a club copy