Here's what we do next. We put to use the biggest economic multiplier per hammer in the game: Jails and switching to an espionage economy. The first steal target was Chemistry, because there was a window open to trade it for Rep Parts. 600 gold is a little hefty, but still much cheaper than stealing RP separately. (By the way, I was considering between Mercantilism and Free Market, but then realized here that Merc was the wrong choice. It would kill that 20% steal discount for a trade route!)
I'll skip going over the details of espionage math. Just know that all the discounts mean the EP cost is usually around half of the beaker cost. And even less in real terms considering EP-beaker skew, which operates just like beaker-gold skew, using the extremely hammer-efficient EP multiplier buildings.
And even though I thought I was deep into WFYABTA, there was still a crack open to steal Steam Power and trade it for Scientific Method.
But then Charlemagne tripped over to Friendly! That was thanks to religion, and after I intentionally traded him all my surplus resources for a while to get the diplo credit for that. Now the trading floodgates were open again. That let me spin...
Steal Steel, trade for Corporation.
Steal Railroad, swap for Physics.
Steal Rifling (didn't get a picture), exchange for Biology. Lincoln had also hit Friendly.
Steal Combustion, swap with Biology for Electricity. (Had to wait until Broadway was built by Lincoln, but that 460 gold was Charley's wonder refund.)
Steal Artillery, not worrying about the lack of a trade because now my EP production could just directly outrace anyone else's research.
And so in 1510 AD, I reached core tech parity. Down by only the inconsequential military side techs.
That despite a GNP number that just won't catch up to the AIs. Even though I now have my EP multipliers up and solid leads in production and food. The GNP leader is India; I have to believe and hope that it's inflated a lot by culture. But anyway, the real indicator here is my massive lead in production with Dikes, and also a decent lead in food just by having more cities.
All my stealing had been from Pericles. Of course, he never caught on to fight back. He would rather spend 5700 EP on the weakest civ on the planet instead of me, despite disliking both of us equally (-3). Anyway, all this stealing evaporated Pericles' tech lead, and the trading pushed the lead to Charlemagne instead. So I switched some espionage over in that direction.
Steal Radio, trade for Refrigeration. Man this is like clockwork.
Steal Rocketry, syncopating the clockwork just a bit by collecting all of Assembly Line, Medicine, and Military Tradition for it.