[Jack21]

Pre '85 289's and 302's used a different firing order than post '85 302's an all 351W's. What determines your firing order is your camshaft.

Find out from your cam Mfg. which firing order it uses, early, or late 302.

If that doesn't work, remove the valve covers, rotate the engine by hand and find out what the firing sequence is by the valve openings and closings.