A word about the gears 123ignition uses. The helix angle — one of the most critical gear parameters — is identical between the OEM and 123ignition pinion gears.

Please Note! - Those with early 1978 911 3.0 SC engines (produced in 1977) need to know about the official Porsche technical bulletin from 1978.
That bulletin specifies that when installing a later-style distributor, the earlier bronze drive gear must be replaced with the updated version. Failing to do so may lead to compatibility issues, regardless of the distributor brand. 123ignition literally has hundreds of the 3.0 SC distributors in service over the past 7 yrs. Not to mention all the regular 911 Bigs like the 2.4 and 2.7 that are successfully in service as well as BMW, and Ford Kent gears without issue. There have been a couple of issues reported that target the SC 3.0. Which the Service Manual specifically states, Early 1978 Porsche 911 3.0 SC engines (built in 1977) were equipped with a different type of bronze drive gear.
When replacing the distributor in these engines, Porsche officially recommends updating the gear to the later version. If the technician has followed the protocol then the block is stamped appropriately. All of which is outlined in the Porsche technical bulletin from 1978. It applies to all aftermarket and OEM distributors — not just 123ignitions.