AFAIK, the 410 never got the 603G series engines!
The only real difference between the A model and the B model was the upgrade to Mk131 13mm mg's verses the A models MG17 7.7mgs.
IIRC,in the books I've read that the RLM put in emergency measures and all aero engines went to single engine fighters first! This left the 410 to continue on with the 603A. They built close to 50 single seat 410 and some of these received Gm1 kits for high alt work,however by the end of 44 they were being withdrawn from service.

PS: AH models the 603 A in both 410,only the weight changes and if you want to save alittle weight opt for the mg17's instead of the Mk131's,I think it's slightly over 200 lbs difference! Fuel loads make the biggest difference as does the "big" gun packages.