Holy sh*t, a RUNNING 350 and TH350 for 200? BUY THAT. You want a game plan? Do this
Buy the 350 for 200$.
Keep your 200R4 and sell the turbo 350, this will supply you with some of the money back that it's going to cost to install this 350.
you'll likely need motor mounts, some exhaust work, probably some wiring adjustments and more than likely some throttle linkage parts.
That 200R4 in your car now, SHOULD bolt up to that 350 with no problems.
The reason im telling you to keep the 200R4 is, A. overdrive, B. I don't think a 350 for 200$ is going to be cranking crazy amounts of power, not enough to toast that 200 anyways, and C. you won't have to go shopping for a different crossmember/ trans mount / driveshaft.
And if you play your cards right, you can get between 150-200 for that Th350. That almost pays for the engine.
When it's all said and done, you'll have a die hard good old chevy 350 that won't let you down, if you treat it right. AND you'll still retain high teens/ low twenty in the fuel economy because you still have an overdrive trans.