What is the internal differance between a 391 and a 390. Just wanted to make sure distributors would interchange. I want to convert '73 391 to electronic ignition from '76 390.

Thanks for any info.
Jicysa

 

I believe the 361 and 391 truck engines use an oil pump with a 5/16 hex, instead of the common 1/4 hex, like the FE series. If I remember correctly the gears are the same, but the pilot in the block is larger.

 

Thanks. I will probably look at the Pertonix Ignitor for simplicity