I have a 1970 350ci with an Edelbrock Performer RPM intake

Edelbrock's site recommends the #60519 cylinder head assembly as the best match

I notice among the differences between the 60515 & 60519 models is that the 515 has accessory bolt holes drilled and the 519 does not...

...what would they be for?

 

Um, for bolting up accessories? That means things like the alternator brackets, A/C brackets, etc. If you are using stock brackets, you need the holes. If you are using aftermarket brackets, you may not need them, depending on the brackets.

 

Uh, what?
Those part numbers are the same casting, both will have all the same holes as stock, and will be tapped.
The difference is just the springs that come pre-installed.
http://www.edelbrock.com/automotive_...ain_olds.shtml

Just to check - you know you can't use a mechanical fuel pump when running the ebrock heads on a small block, right?

 

See I was looking here
http://www.summitracing.com/parts/edl-605119

About halfway down "Accessory Bolt Holes Drilled: No"

Whereas on these http://www.summitracing.com/parts/edl-60515
it says "Accessory Bolt Holes Drilled: Yes"

Does Summit just have their info posted wrong?

 

I had worked that much out on my own lol, was just looking for specifics - the phrasing struck me as odd, wasn't sure what all else they may have been referring to

 

It's not the first time that the catalogs would be wrong.

The only chance is if the 605119 - being a polished piece instead of the normal 60519 - omits the bolt holes for aesthetics. That would be deeply surprising.

"Accessory drive" is an awfully common phrase.