So back to the topic, no one has any idea how LGBTs voted pre-1992? I mean it's not like the Democratic Party has been the clearly more pro-LGBT party before about 2000 (which is the OP's point).
Still I think that the gay community tended to drift towards the Democrats by default beginning probably in the 70s just because they tended to be clustered in urban areas and would have been more likely to form pressure groups within the Democratic Party, Reagan's reaction to AIDS I think was the tipping point even if Democrats in the 80s were really just as bad.
I could see Ford possibly doing well in 76 just because Carter was the one perceived as a bible thumper and probably seen as less gay friendly at that point.