3-on-a-strip conundrums

So...my otherwise good Supro reissue that I use for slide is somewhat let down by its made-in-hurry tuners.

If I could get drop in replacements that didn't involve replacing bushings then I'd be all for it.

However, the range available is both sparse and confusing.
As far as I can tell:
They all have the same post-post spacing and post height 
"Modern" posts are 6mm (which mine are) ,
 Anything "vintage", "deluxe" , or "vintage deluxe" are 6.3mm
Most of them seem to be sold/specced on bushing size rather than post size :(

Any clues on what I need to double check to make sure something I buy will definitely fit with the existing bushings?

Also, it seems I'm not going to get a match on the plastic buttons so...are they swappable?

Thanks!

I recently swapped the 3-on-a-strip tuners for my Gretsch Gin Rickey, and they were a drop-in part - everything was identical. Buttons were slightly larger, but OK.

See here: https://www.thefretboard.co.uk/discussion/260710/3-on-a-plate-tuners-all-standard-size

I have a set of replacement 3-on-a-strip tuners. I had hoped that they would transform my 1965 Gibson Melody Maker into a gigworthy instrument. Turned out that the post spacing was out by a gnat's. I was unwilling to cut into the headstock.

A better option might be to dismantle both sets of machineheads then, fit the new gearing parts to the original back plates.

Thanks all - I think I'll wait til the next string change, whip them off and measure everything, then see what matches.