You need the proper outdrives and bearings.
The gen3 vega is made for the B4.1, which is metric.
And the outdrives have an edge the bearings sit agianst making it wider, the b4 outdrives don't have that.
B4 :
http://www.amain.com/rc-cars/team-as...-asc7668/p8041
B4.1+
http://www.amain.com/rc-cars/team-as...sc9852/p165878