the latch isn't the problem, it's bolting a behemoth like that to the sheet metal without having that area properly supported. 4runners are not set up for that.
Aha.... the top mount. How about grinding off the left portion of the top mount? The only reason we have trouble mounting the JDM swing out is the latch which is mounted to the rear door in a surf. I am now in search of a montero swing-out.
Montero Sport's with the rear tire carrier are quite rare as-is. Finding one might be difficult and would require a fair bit of fabrication to mount onto a 3rd Gen. I'd keep saving for the JDM unit IMO.