... the part no.s are the same... except for the first bit being 3VD/4TX. So is it safe to assume they are the same?...
No.
This site explains the structure of Yamaha part numbers.:- https://thumpertalk....a-part-numbers/
That shows that the first bit (your 3VD / 4TX) indicate the first machine the part was used on. So logically the parts are not the same or the 4TX model's part would show as a 3VD.
The second bit identifies the part by its description (your handlebars...) and that number will be used for that part from any bke.
So all you are seeing as being the same is the code for the part, not its definitive model-specific version.
However, just because the part is not OE doesn't mean it won't fit!!! That's where the knowledge of folk here may help - but not me.
Honda has a similar system where the first part is the first model the specific part was used on, and threw up some useful sources of spares for my (pre-TDM) VFRs, and for my CBX now it is getting on a bit and parts are harder to find.
Edited by steve27bha, 17 March 2021 - 10:37 pm.