I'll take a crack at it but my knowledge is limited. Hopefully others with more detailed info can pipe up as well.
All the model #'s you have listed above are designations for various XT600/Tenere models in europe.
34L is the original xt600 Tenere bike with the huge 30L tank. mechanically very similar to the 1984-89(43F) xt offered here in N. america.
1VJ and 3AJ tenere models are later in the production cycles and have various changes that are either upgrades or downgrades based on the speaker's point of view. Don't know much about these as they were never offered here and I've never seen one in the flesh.
43F is the original xt 600 (1984-1989) like we have here in CAN/USA, offered in red/white paint. Distinctive characteristics are 18" rear wheel with drum brake, small (10L) gas tank, separate oil tank at left rear subframe, kickstart only. This is the model I have(1986 xt600 canadian machine). Cavet: I believe in 1988-1989 years the motor changed somewhat (barrel/head design changed slightly) possiably other changes?????
xt600E in n. america 1990-95 typically blue in colour with grey frame, 17" rear wheel with disk, lowered suspension, electric start, crome steel wheels vs. aluminum on the early generation. Oil resivoir is now in the frame's headstock.(funky early 90's pink and sometimes aquamarine green graphics) How this machine meshes up with the mechanicals of the IVJ-3AJ ect. of the european bikes is unknown to me.......
N.am TT bikes are said to have A nickisil coated barrel vs. the steel liner(confirmed) on my XT????
I really don't know what the european designation is for a basic TT600 like your's????? Perhaps some one else knows.
I have changed the oil pump on my machine and have documented the processs here in postings. I would be reluctant to recommend you do the changes I went with because I just don't know if there are any differences that might pose a problem on your TT. My gut feeling is the bits required are exactly the same but......I just can't say that with certainty. I found it very difficult to track down correct info about this swap. The info is out there but is spotty and incomplete. Some members were very helpful in steering me in the right direction. My pump has been in for a while and dooing it's job well.
There is one fellow I know who can confirm the model designation of your machine and sell you exactly the correct bits to do the oil pump swap.
Dave Lambeth in the UK. I've bought stuff from him before and suprisingly the parts are not much more $$$ than buying them here. In speaking with Dave you will likely learn quite a bit about you're machine He is a Yamaha XT/TT guru.
I hope some of this is of help to you! Should be clear as mud!