I saw a very affordable 308 lower the other day and almost bought it. I don't have a 308 jig though. So as far as I can tell the fire control pocket and holes are basically the same as a 5.56. I don't have a 308 to reverse engineer off of. So are the fcg holes the same relative distance from the take down pin or mag catch as on a 5.56? DPMS based lower btw.

No.

try this: http://www.hellfirearmory.com/image/cache/data/AR-10%20Receiver/AR10-prints-917x1000.jpg

I've seen quite a few variations in 80% AR308.

Here's most of the info I have.

So the fore and aft measurements make sense, but the elevation is confusing. A simple measurement from the deck to center of each hole would be easy. Are the fcg holes the same distance from the top as on a 5.56?

I have milled 14 AR15 rifles now and I would not attempt an AR10 without a jig....

As  seen below there are multiple relationships of the selector to the takedown holes from different 308 lower manufacturers. The real key is, all 80%ers have the selector detent hole in them when you receive them and the rest of the trigger pocket and trigger holes must work from that point. Yes, the relationship of the selector to all of the other trigger pocket machining is the same on the 308 as the AR15