On the 1982 and 1984 Senate elections, OTL the Democrats made no net gains at all in 1982 (they retook one seat where the Democratic Senator had resigned and the appointed temporary replacement had been a Republican), and did make net gains in 1984. It was widely noted at the time in 1984 that Reagan had no coat tails, the presidential vote really seems to have been due to personality. Someone made a good catch with Kentucky, Mitch McConnell unseated a Democratic incumbent and with Bush instead of Reagan that race might well have gone differently and produced butterflies. I can't think of any other races that would have changed. Incidentally, Al Gore entered the Senate in 1984, unseating a Republican incumbent in a state neighboring Kentucky.
I'm pretty sure that the gap between the party vote for president and the party vote for federal legislature in individual races set some sort of a record in 1984.
OTL the Democrats gained 26 seats in the House in 1982 and lost (I'm not looking this up) something like 14 in 1984, and ITTL you reduced both numbers are are left with about the same net gain over the two elections, with no individual races that might change having later repercussions.
Also, OTL under Bush, the Democrats gained seats in both federal legislative chambers in 1988, 1990, and 1992, so the elder Bush didn't have any coat-tails either. Really, since Reagan took office, only the younger Bush has had any success among prezzes in transferring whatever personal popularity he had to legislative candidates. Otherwise, holding the White House has pretty consistently turned out to be a disaster for the party in down-ballot races and this was true for Reagan too.