Reagan was pretty old by 1984 to be elected for a first term.
Then again, coulda, woulda, shoulda,
McCarthy might have attracted some eastern GOP libs but that's all. He was a distant man, more stand offish than Nixon and even more tone deaf, and could never have mounted a serious campaign.
If Ford had been reelected in 1976, he would have been ineligible to run in 1980. He acceeded to the presidency in August, 1974 -- more than two years' worth of Nixon's term. So he was eligible to only one additional term in his own right.
In 1980, Dole would have been the incumbent Vice President, so presumably he would have had an advantage. Again, coulda-shoulda-woulda.
History will treat Gerald Ford kindly, and it may not have if he had served another four years. As someone else pointed out, that could have prevented a Reagan presidency. As I see it, and I liked Ford, and loved Reagan, it was a win/win situation for us as it turned out.