69 Dart Hard to Start When Hot, Starts Fine Cold. Vapor Lock?

My experience with slanties is that they are very difficult to flood.
When mine got ornery, I just pumped the intake full of gas, floored the pedal and cranked it! It never failed to start.
But when the compression goes away, they don't suck no more. Well they sorta do, but if the fuel ain't in the air coming past the throttle-valve, well, whatever is laying on the floor of the plenum is gonna stay there until the engine fires up, and then, the fast idle better be working ...........
In your case, I would start with a valve adjustment, followed by a compression test.
Neither of my smog era slanties ever liked the factory lash settings. I "hot" set mine to .013intake and .023 exhaust, BUT
on every old slanty I ever had, the valve stems had beat grooves in the rocker arms and the lash could only accurately be set with a narrow enough feeler that properly fit into that groove.
I say hot-lashed but, by the time I got the plugs out and the VC off, she wasn't hot any more; so she just got what she got, and the lash I used just flat worked. I went into the job having previously marked my balancer for TDCs of the various cylinders, so, I just used TDC for setting the lash, as each cylinder came up, in the firing order. Thus lashing only takes a couple of minutes.
If I set the exhaust even just a lil tight, I had problems. However, I run all my engines at or just over 195 on the IFR gun, so that might have something to do with it............