I just made a similar repair to my wife's RV-4. The mount was cracked in several places and the gear toed out. The tires had quickly gone bald, leaving black marks on the hangar floor. It took a lot of effort to push the plane on concrete.
The inner two mounts which support the upper end of the landing gear sockets were pulled forward. The large angle aluminum brackets for the mount bolts had sheared the rivets to the deep longerons (keels) and the firewall rivets were pulled through in the toe box. (The 2 vertical rows between the rudder pedals)
The firewall was pretty sad looking, but in order to keep the job on track I elected to keep it and forged ahead. The 4 corner longeron weldaments are the newer type and still good.
Russ McCutcheon makes weldements for VANs, and rebuilt Marilyn's mount in 3 days. Russ was great to work with, and will give you a tour of his shop, plus educate you on the repair process. He is a dedicated craftsman. The rebuilt mount fit perfectly.
All the bad rivets were drilled out #20 and replaced with AN525-832R screws which have un-threaded shanks for the grip area. These are low profile washer head screws which are substantially stronger than a -4 rivet. I was able to re-install the angle brackets and pull the firewall back into place using jet-nuts or lock nuts. The firewall pulled back into place rather well, although cracks remain and are sealed.
While the engine was off, I removed the sump & gearcase for cleaning & inspection. I also replaced the crankshaft bolt. I installed rebuilt mags & plugs, fuel pump & carburetor. Additionally, I welded up a hole in the exhaust caused by rubbing, and replaced the missing exhaust support strut that caused the leak.
The tires and tubes were replaced and the brake calipers rebuilt. The left wheel pant inner mount plate was renewed. The wheel bearings were repacked and the seals inspected.
Once disassembly starts, 'Discovery' begins...and the work piles up!
Marilyn is the 9th owner of this plane, which has about 1500 airframe hours. It took about 3 weeks to get her back in the air.