There's a quasi-famous speech Buckley gave, with Reagan in attendance, where Buckley says Reagan is the political figure he admires most in America.
I'm not certain of the date, but I believe Buckley said that before Reagan ran for president.
I think I was mistaken. For some reason, and I’ve tried looking, I thought NR was supporting Bush over Reagan in the 1980 primaries and Ford over Reagan in 1976 but I can’t find anything.