KKPIT (chinese knock off manufacturer) had actually made some high quality machined nylon 43T spurs that were designed for the Tekno, but I have been unable to find them the past couple years.

Yes, as will the EB48 original onto the EB48.3

ok guys I look and looked and can't find a solid list on what it will take to move a eb.3 to a complete .4 I know it is not going to be cost effective but can it be done.. and if so a parts list would be incredible.. thanks in advance I know some one out there has this info..

Just off the top of my head the major things that are different;
-chassis
-front and rear arms
-front and rear drive shafts
-steering Ackerman/geometry
-front and rear ring and pinion gears
-front spindles

I think they list the differences on the website; https://www.teknorc.com/shop/tkr8000...ed-description

Honestly, I like my .3 just fine still!

How much radial movement is acceptable on the center diff bearings? Mine still turns nice and smooth but there is what seems to be too much movement. I never saw it new so I don't know if amy movement is normal. Mine is really loud at speed and I had thought this was due to the steel spur gear but now that I have seem this movement I think it could also contribute to the noise and probably doesn't help the wear characteristics either.

So, is there a spec on what I should see? I haven't put a guage on mine but I would guess that there is 0.5-0.75mm.