I'm thinking to replace the original carb with a VM34, I would like to retain the autolube. Any suggestions on vendors, etc. I definitely only want to go genuine Mikuni

I am surprised that I've had no replies to this at all... it seems like a very common issue/question. Is this a case of 'dude just search the forum...'

The specifications on most Yamaha carbs are "proprietary".   Dimensions and features are often significantly different than a "generic" Mikuni.  

For example, I'm pretty sure you have a "tall cap" Mikuni so at the very least some sort of throttle cable modifications will be needed.  Inlet diameter, body size, body length, and outlet diameter can be different on a Yamaha spec carb compared to a generic Mikuni.  

Not very common to need a new carb unless the slide bore is worn out (rare) or the body was damaged or badly corroded.  Jets and slide needles can be replaced with Genuine Mikuni parts (slide needle, needle jet, starter plunger, and float valve are usually the only parts that ever wear out)

I have a brand new Lectron carb I had made for my 77 DT400 and never installed.  (Son of the owner bought his Dad's favorite bike back from me).  Lectron dimensions were machined to match Yamaha specs and will bolt on but cable would need to be modified.