There weren't as many polls back then. In any case, the final pre-election Gallup Poll gave the GOP a 7% lead. FWIW,the last election that had a final lead equivalent to the one you mention above was in 1974, when the Democrats had a 19% lead.
Here were the margins in the final Gallup generic congress polls in midterm elections, along with some additional interesting stats: Gallup Polls.
2002: GOP +6
1998: even
1994: GOP +7
1990: Dems +6
1986: Dems +12
1982: Dems +10
1978: Dems +10
1974: Dems +19
1970: Dems +6
1966: Dems +4
1962: Dems +16
1958: Dems +16
1954: Dems +4
1950: Dems +2
All are likely voter figures except for 1986, which is registered voters.
A 19% lead when you already have 250 seats, or whatever, translates into less than when you have 200 seats. What the GOP has going for them this time is more sophisticated campaign techniques, and gerrymandering. Will the dike hold or not?