Ace stocks are good, it's their customer service that some feel leaves something to be desired.
Ace has taken a bad rap for long shipping times, and in at lease one case, not keeping replacement parts for a older model of stock.
I would like to tell you this: If you want to cut off the tang to install the internal block - don't, and here's why. (my opinion only of course)
I put a collapsable ace stock on my polish tantal. After researching I decided I didn't want all that extra crap (external block) hanging off my rifle.
Thats cause I'm picky, and I'm betting your picky too. Now here's the point, while the internal block does look better than the external, it still leave an ugly spot.
It also took some fitting because it interfered with the selector and the rivet stub for the rearmost triggerguard rivet.
If at all possible, I would go with one of the rear trunnion blocks from AKBuilder that is made for Ace stocks:
AKBuilder block
Going this route would certainly be more work: drill out the old trunnion rivets and weld them up; drill new rivet holes for the new block, rivet the new trunnion, refinish rifle. But the end result will look much cleaner.
And that's exactly what I'm going to do exept I'll be replacing the receiver on this particular rifle (POS ITM receiver)
So to summarize I cut my tang and now I regret it. Don't be like me
PS: I replaced the collapsable stock with one of their fixed ones - and I like it much better.