I need an update
 

Can some one advise me please ?

Having not raced off road for years ! Could you tell me is there still a stock class at meetings ?

Generally speaking..no....all open/modified.... However some individual clubs do run a stock class or even a brushed motor class.
Check with the club you intend to join.

There's nothing wrong with running a 13.5/10.5 in modified when you're just getting up to speed again :)

My kid ran a 10.5 and he was fine, when he got used to it we just boosted it through the ESC and was able to keep up with the faster cars on the straights.