Green’s Dictionary of Slang

often in pl., modification(s).

1943		C.H. Ward-Jackson It’s a Piece of Cake 43: Has this Wimpey got the new escape gear mod?
2003		J. Nelson ‘The Shipbuilder’s Special’ in Vette Mar. 🌐 Before the body was re-united with the frame, modifications were needed to accommodate the new powerplant and gearbox. [...] When the mods were finished, Rob and the Roscioli crew sprayed the body with PPG White Diamond Pearl paint.