I'd definitely vote for 2 classes, but I'm not sure anymore which option is better.
Restricted GTRs have more sense, being rwd, being like Super GT etc, but they don't really have appeal, do they. Who would want to race them? They are not used anywhere else, they are not really new class, just slowed down big cars. But they are a new challenge for sure, and that's not a bad thing. It's a new aspect of LFS, to have cars "made" for the league.
Problem in distinguishing between classes isn't really big problem. In Super GT there are same type of cars in both classes and I as a casual viewer have no idea which is which until they get close on the same straight and we see speed difference. Whatever solution admins choose would be ok and enough (number ranges, names colours, marks on skins...).
FWD GTRs seem good idea too since there are quite some teams who are good in them (and usually they don't drive big GTRs much), everybody knows them well, two seasons of LFS GT were driven like that and were good (mostly). Competition might be better because of that, and it's nice that they are totally really different cars. But FWDs being FWDs aren't really endurance cars.
Differences in speed are not an issue as admins said, they would only choose the teams with capable drivers and would penalize those who can't handle the traffic.
Perhaps a useful poll would be which teams would really enter restricted GTR class and which would enter FWD class? As I'll be driving GT1 I don't mind either, but those who voted 2 classes would they really drive what they voted for in 2nd class?
In the end, I prefer restricted GTRs, and I'd like to drive that if I was in GT2, but FWD option is more feasable for most. So, I don't know. I'll vote for restricted GTRs just because it has less votes.