You can see the factory mount sits fine and bolts up fine.
With the 4l60e lifted out of the way the hawks mount would go in in the front but is too wide in the back without really forcing it. Might have worked if I cut those pieces off after the bolt holes
Yet at the same time it doesn't appear wide enough. It hits the trans pan on the passenger side. And while I don't have a pic of it I also tried dropping the pin through first and then raising it up. You can see when I lifted the trans out of the way and just bolted up the passenger side how big of gap there is between the frame rail and the cross member. When I hold it tight to the driver side the passenger side shows more of a gap.
In one picture you can see I forced it. Started the front two bolts and then used the impact to try and force the other bolts in straight. You can see the bolts are at the limit of their slots and this was with the trans raised out of the way. Darn near cross threaded the bolt holes to get that pic. Had to use the impact to put the bolts in at an angle and then force them straight with the impact before running them in..
Then I laid it over top the stock mount. You can see if I align the actual slots the hawks mount is way off. If I do my best to center everything the hawks and factory slots don't line up with the stock crossmember.
Hawks just claims the frame of my car must be tweaked. To me it's more like their crossmember wasn't welded right in the jog of the factory one wouldn't work so easy.
Very disappointed they wouldn't send me another that was maybe welded right like I asked and blamed my frame because I sent them all these same pictures.

 

When i put mine in I had to "make my own bolt holes" to mount it. Mine was an 82 and i think earlier cars didnt have the same pattern as later cars. I just drilled large holes an welded nuts inside that frame rail to attach the mount where needed. I also had to raise the brake/fuel lines up a bit, i also grinded some extra material off the top to make it fit better

 

82-84 is different. This is a 91. Not even the first 91 I've swapped

 

Gotcha also remember mine was an inch off to one side so i welded hole shut and drilled another. Theres been other threads and its conclusive this is not the best mount. I believe most others have had to do some fab work to it.

 

I had those exact same issues on my 84 with the same hawks mount, so its not a year specific issue. Elongating some holes and relocating the center one trying to make it fit and this was back in 2016. So not much has changed since.

 

Sounds like Hawks is the one who had a bent/tweaked frame and then made a product based off it. I don't demand perfection from aftermarket suppliers, but it's nice to have good customer service support when things aren't quite right.

 

I got a 2nd mount but it had the same issues as the first.
So here's what I did and more specifics where it doesn't fit right.
At first I thought about cutting it in half and welding it back together, and that might work, but the bolt holes are so far off from the factory mount(see above pics) I figured I might have to still cut out bigger bolt holes, so I avoided cutting it in half.

With everything out of the way it is physically too wide to fit between the frame rails that you can't push it up by hand, yet at the same time the bolt holes aren't wide enough to expose the factory captive nuts on both sides at the same time.
I notched for the trans pan on the passenger side. This I maybe could have gotten away without doing but it makes it even harder to get the mount in and out past the transmission pan.
You can see at the same time on the passenger side the bolts are at the extreme outside of the slots. Even still I had to go to the driver side and cut out the bolt holes wider so the captive nuts in the frame where fully visible.

On the driver side I cut both the top and the back of the mount off because the frame get's narrower as it goes up and also back. There's even a lip that comes in narrower I pointed an arrow at in the pic. In the pic only the back of the mount has been cut off and you can see where it was rubbing paint off trying to install. The arrow points to the lip and why I cut just above the weld line off as well.

For the single trans mount pin it's a 4thgen 4l60e and even though the oil pan is up against the k-member I still had to extend the notch to the back. Even with the notch extended it still angles the mount and pin toward the front so the whole slot really needs to be back a bit. It will put a constant strain on the transmission mount and over time being rubber I can see it cracking quicker.

With all that cut. I was able to lower the trans. Attach the trans mount pin to the crossmember. Then I raised it enough to start the driver side and the cut up passenger side holes. At that point I used an impact to run the 4 outside bolts down as the mount is still to wide fit between the frame. It's still not something that will easily go in and out by hand.
My other 91 has a Skulte mount but of course they stopped making those over a decade ago.

 

I had to clearance mine on the passenger side for the transmission pan, but I didn't have any problems with the bolt holes lining up.

 

Looks like a piece of junk to me.