Spofforth and Darley will contest the 2016 Atkinson Swires Cup final after impressive semi-final wins at the weekend.
Spofforth, who are eyeing a first cup victory since joining the Nidderdale League, bettered Birstwith by 17 runs in a match that saw more than 600 runs plundered.
Nick Robinson (118) and Andrew Bottega (121) shared a doubled century stand to set Spofforth up for a massive 309/9 in the first innings, although Birstwith battled back.
From 221-1, Spofforth lost eight wickets for 88 runs with George Hirst (3/67) starting the collapse.
Birstwith's reply got off to a solid start as captain Jon Millward (27) and Tom Croston shared 53.
Following Millward's dismissal, Croston kept the scoring rate high alongside James (63) and Dan (43) Riley. However, the chase ran out of wickets in the final over with the score on 292.
Darley were originally knocked out of the competition by Harrogate 3rds in the quarter-finals but found themselves reinstated due to Harrogate fielding ineligible players.
Duncan Naylor's side are hoping to win their third cup victory and first since 1994, when successfully defending their first triumph.
In-form batsmen Chris Gill scored an all-important century as Darley amassed 261/9 against Helperby, with wicketkeeper Rob Hainsworth adding 46 late on.
The pressure of runs told on the visitors as they were bowled out for just 118 in 25.1 overs.
Rory Sands collected the best figures of 4/25 as only number ten Tom Spilman put up any sort of resistance, finishing unbeaten on 30.