Bell-Toxtle, 20, had a spell on loan at the Gingerbreads last season from Basford United, while 24-year-old Broadhead spent the campaign with AFC Mansfield.
Broadhead said: "I'm really pleased to sign for the club. Grantham are a big club and I was delighted to get the call from Paul. He's explained what he wants from the squad and how we need to get to up to speed very quickly. I'm looking forward to getting to know everybody at the club and hearing the supporters I've been told about!"
Bell-Toxtle said: "It's great to be back. Everyone made me feel really welcome last season. Paul and Russ are pretty clear in what we're to expect as a squad. Obviously, I know Greg (Tempest) from Basford but it's going to be good to get to know the new squad during pre-season and give the season ahead a real good go."
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