it's a simple NS switch.. it looks for the range selector to be in neutral before you can start. if the wires are good and it is causing problems, it's either the switch or the switch not getting moved enough. the 65+ machines used them..
53 1 C5NN11N500A SWITCH Switch, Starter Safety, Years: 01/01/1965-09/30/1966 53A 1 9672467 O-RING O-Ring, .562" ID x .103" Thk, Years: 01/01/1965-09/30/1966
53B 1 C5NN11N005A SHIM Shim Pack, Switch to Shift Cover, U.S., No Longer Serviced., Years: 01/01/1965-09/30/1966
54 1 C5NN11467H PLUNGER Plunger, Starter Safety Switch, W/Pressed Steel Cover, Red, .990/.995 (25.146/25.273mm), No Longer Serviced., Years: 01/01/1965-09/30/1966
54 1 C5NN11467J Plunger, Starter Safety Switch, Red, 1.315/1.320 (33.401/33.528mm), No Longer Serviced., Years: 01/01/1965-09/30/1966
55 1 C5NN11N520A ROLLER Roller, Starter Safety Switch, No Longer Serviced., Years: 01/01/1965-09/30/1966
56 1 C5NN11N517B Connector, Starter Safety Switch, U.S., Procure Locally, No Longer Serviced., Years: 01/01/1965-09/30/1966
soundguy