Recipe translation from brewery to brewery

I have a quick question regarding following someone else's recipe.

When you see a recipe posted, quite often I find that there's no indication of the efficiency of extraction for the poster, nor an indication of the SG of the beer.

So my question is, how do you follow someones recipe, when you have no idea what you're actually shooting for in terms of the SG.

eg. Tom posts a recipe for 14lbs 2-row (100% efficiency in 8 gallon mash = 14*37/8 = 65points or 1.065 SG). Lets say Tom has an extraction efficiency of 80% (52pts or 1.052 SG). However, I want to copy this recipe from Tom, but my home efficiency is only 60% (39pts or 1.039). Therefore, if I copied the recipe verbatim, I would be well off on the SG, and subsequently ABV since I have significantly lower efficiency in my setup than Tom does. To get the same starting gravity, I would have to use much more base malt (~4lbs more).

So my question is, how do you copy someones recipe when you have no knowledge of their efficiency or the SG. Do you assume an efficiency (say 75%) and go on that?

I am new to brewing, so please forgive the ignorance of this question.

Most of the recipes I have seen, at least on here have the efficiency listed in the original posting along with the OG and FG numbers. I also input the recipe into my brewing software, this lets me adjust it to match the original against my usual efficiency and also to adjust the hops to match the IBU using my AA% hops

For instance, the Black Pearl Porter and the Bee Cave Porter...neither of which have any indication of SG or efficiency. So where do you start with a recipe like that since you dont know what you're shooting for?

In the event that someone forgets to post gravity readings, someone else has almost always asked. Yes, they do tend to be important, as you've discovered. The Bee Cave porter has gravity readings posted in post (not page) #4 of the recipe thread. I didn't check the other one, but I'd be surprised if it wasn't in there somewhere.