MP DISTRIBUTOR TIMING CURVE 340

What carb?
The engine is no longer near stock, so stock timing curves go out the window. That is why the engine is going to need 20+* for best idle.
If you want to dial in the timing curve with this modified engine, it has to be done on a dyno; anything else just becomes a good guess, which might be good enough.
I have run plenty of carbs with the t/slots closed off....& never had a problem. Many TQs & AVS carbs had bypass air holes in the base which can be blocked/reduced in size to correct the T slot position. The problem with T slots is when there is too much exposed at idle.
PCV can be run from front or rear of carb, whichever is more convenient. It is all manifold vacuum. On Pontiac V8s, the PCV does not connect to the carb. It goes into a junction in the intake, about 2" in front of the carb. The junction accesses both planes [ dual plane intake ].