Paint the mark on the harmonic balancer with paint -choose 10* or 14* or something else if you have NO2 or other power adder. Advancing the timing beyond 10 * gives more low speed kick when you stand on the accelerator.
Be prepared to always run Premium gas (92-93 octane or better) if you go past the stock 10* timing.
If you don't, you'll get pinging or detonation which can damage the engine if it happens for a sustained time.
Remove the SPOUT connector (do a search if you want a picture of the SPOUT connector) It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT Warning: there are only two places the spout should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.
Connect timing light up to battery & #1 spark plug.
Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.
The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8
got mine set at 13 and usualy run 89 octane in it.
Ditto on putting the spout in your pocket, I set mine on top of the radiator one time, got lucky when I stopped to see why it was running like crap.