I've got a Bing manual and except for the main jets, all the parts are the same for both carbs .
It shows a 138 main or the -348 and 135 for the -353 .
Just make sure both main jets are the same .
My '81 R65 came with 145 main jets and I put 138's from my spares from one of the LS's I have .
I've seen no difference in engine performance, or fuel consumption with the smaller jets installed .
If by chance you can't get the numbers from the Bing site, here's what I found in the manual .
Main jet, whatever you decide on, needle jet 2.64, jet needle 251, atomizer 591, idle jet 45 .
If you replace the jet needle, that's needle that is installed in the slide, the position of the needle is 3, that's numbered from the top .