I don't know if you realise how incredibly lucky Ronald Reagan was that he could run for President in the perfect storm that was the election of 1980, and how utterly
unelectable Reagan would be without that ideal set of circumstances.
Pretty much any credible Democrat wins in a landslide against Reagan, who's easily painted as a far-right extremist. Bear in mind, even in 1980 it was close up until Election Day
because of Reagan, not in spite of him. The nation was wary of his Goldwater-with-a-smile politics.
Indiana's
really iffy, and there's not a chance in hell Reagan's winning much of what Moderate Hero (tm) Gerald Ford won outside of his western base.
434 - 104.
PS: Although Oklahoma is one of the most Republican states in the country on a national level today, IIRC Carter lost it relatively narrowly in 1976. I could be wrong, though, so feel free to subtract 8 electoral votes as you please.