Hi Norm,
I do not think that yellow colour is factory either. I wonder if its orange or grey underneath? Does it have the chunky top to the area over the blade disc? Mine is smooth.
I guess if the air gap is out you would have to check for play in the bearing in this model with belt drive. I do not think the engine itself is any different on the VEX 60. Just manifold and perhaps exhaust mods to get a little more power. You could change over all those.
Looks good so far to me. Very neat with no sliding plate.
All the best
Jeff