The Pilgrims head to the Brewery Field (kick-off 3.00pm) to take on the National League North outfit, who were divisional rivals up until last season.
United have reached round five courtesy of victories either side of Christmas – beating Alvechurch 1-0 at home and Gateshead 3-1 at Stockton Town.
Spennymoor, meanwhile, were 2-0 victors at Hampton and Richmond Borough in round four, following opening victories over South Shields (2-1) and Alfreton Town (1-0).
The Moors, managed by Graeme Lee, are currently 11th in National League North, sitting seven points outside the play-off positions.
Should the scoreline remain level at the end of normal time, the tie will head straight to penalties.
LIVE COVERAGE
BBC Radio Lincolnshire full-match commentary, courtesy of Rob Makepeace and Christian James, is available.
X updates will be available via @bostonunited throughout the afternoon.
TICKETS
Tickets for away supporters can be purchased here.
KIT WATCH
United will be wearing their third kit of raspberry and rhodamine red.
PIC: Chris Bray.