From MY experiences only.
If you want to run 14-16 degrees of initial timing on a 351C, you'll need to make sure the mechanical advance is NO MORE than 20 degrees on the crank. This has been hashed out many times in recent months. 20 degrees crank equate to a 10L slot width or .410". This 20* plus the 14-16 initial = 34-36 degrees max mechanical plus maybe 6* vacuum advance. This is what I found worked best for my 351C 4V M code with 10:1 comp on 91 octane Shell gas. That adds up to a hard pulling motor and zero ping (spark knock). My distributor is a Motorcraft original that was rebuilt completely and with a modified slot as described and I use a Pertronix Ignitor II module with matching Flamethrower coil. Springs are 1 Mr. Gasket 925D and 1 factory original heavy spring. My alternative choice would be a Duraspark. These can be ordered to match your engine and cam I think from Performance Distributors.
I have a friend who bought one of those Chinese pieces of crap HEI things and it nearly cost him his motor. He ordered it for a 351C but the gear was for a 302 even though it was labeled as for a 351C. If you want or must go with an HEI then make sure you know what your buying. Personally I think they look like crap on nicely dressed 351C, just my 2 cents worth and I do realize some like just plain gordy!!
Geoff.
