Through the years I have dyno tested several engines that came out of cars with very similar stories.

It was almost 100% of them making noticeably less power than expected......... and the car running on par with the results from the dyno test.
I can think of a couple where the owners each spent several thousands on parts for the car in an attempt to find the missing ET.

The other side of that story is....... one of my friends had a converter fail on his S/G car.
Bought a new high dollar unit from a big name supplier.
Car was waaaay down everywhere.
Sent it back, they adjusted it...... no change. This happened several times.
Everything was off. 60’, ET, Speed.
Had this been a new untested combo........ we would have suspected the combo was just off.
But the car had run way better for years previously, and ran what it “should” have.

Eventually, a converter was sourced from a different supplier, and the 60’ and ET came back. Speed was still down........new converter had enough slippage that the engine was on the limiter before the finish line. With the original converter, the speed was up 4mph and the engine never touched the limiter.

My suggestion is to dyno the engine.
At least then you’ll have the info needed to know what the car “should” run.

Two comments about what I see.......

Nowhere near enough stall(5000)

Looks like the bump steer situation really could use some attention