OR Maybe if you are lucky,
The updated turbo water pump USUALLY has a "
WHITE' plastic block off plate that can be seen from the front of the engine and this should give you an indication if you have the 46.2mm waterpump idle roller. Not a firm guarantee but usually yes.
Block off plate for the updated pump;
1987 Porsche 924 S Coupe - Water Pump, Thermostat & Hoses - Page 1
This is different from what thomasryan mentioned---the guide plate under the belt covers...
1987 Porsche 924 S Coupe - Camshafts & Timing Chains - Page 2
J_AZ