So many updates.
New thermostat arrived and went in without hassle (except that the gasket they used was made out of super glue and frustration, and refused to come off). I did still drill a 1/16" hole in the flange for good measure. No more pressure backups for me. The temp isnt as steady as it was with the old engine, it ping-pongs between 160 and 185, whereas it used to be pretty steady. But I guess as long as it stays under 220 I'm ok with it.
Also, new torque converter went in. It's a custom unit that a local transmission shop whips up by cracking open a stock unit (I think from TH350 equpped Vegas) and using some black magic voodoo wizardry, matches the internals to the cam and carb that you're running. The unit is then furnace brazed back shut. All I know is it worked. The shop says the stall should be somewhere in the neighborhood of 500-600 more RPM over stock, and the smaller size units the Vegas ran helps keep heat at bay. It definitely feels better...no more rocking at stop lights and the engine actually idles down appropriately when coasting at speed.
The stalling issue wasn't corrected though. I had previously been convinced that the TC was to blame for the stalling issues I had at a stop, not allowing the engine to spin freely when idling. I was wrong. I called Blueprint techs again, shared what I was dealing with and asked for some advice. I had assumed that they dialed in everything between timing and fuel delivery for max HP, since their engines are dyno'd before shipping. The guy chuckled when I mentioned this. Essentially, because they can't begin to predict all the variables in the builds their engines are going into, they basically just get the thing running, ensure it's timed somewhere near optimal, and that the HP numbers are within a reasonable ballpark to what's advertised. Once that's established, the send it. He suggested I check base and total timing, and adjust the idle mix for max vacuum.
So I did.
One thing the Blueprint tech suggested is that I permanently disconnect the vacuum advance from the distributor. They have to connect it for emissions laws internationally, but they feel you are better off without it, they just can't put it in writing...because laws. So it was removed. I then connected a vacuum gauge to that ported vac source and dropped curb idle till the gauge read juuuust off of zero, indicating the transfer slots were nearly covered. This should stop the dieseling.
I then attached my timing light which has a digital tach, and fine tuned curb idle to get to about 750 RPMs. The initial timing was spot on the factory spec, at about 12° BTDC, but total was low, only about 29° at 3500 RPMs, so I bumped timing up to 34°, where Blueprint suggests it be set. Weirdly, idle RPMs didn't really fluxuate much, only came up about 25, but I still pulled it back down again with the curb idle screw.
I then reset the idle fuel mixture by bottoming the adjustment screws and brought them both out 2 full turns. Vac gauge wasn't super steady, but from there I adjusted the mix to get what appeared to be about 13 inches, which was is as much as I guess I could hope for with this cam.
All that work paid off though. After buttoning everything back up I went for a drive. The stalling issue is gone, and with the transfer slots covered, no more dieseling when shutting her off. SUCCESS!
But the raw performance is what really blew me away. The new motor defi packed a lot more punch compared to the tired and smokey 350 I pulled out. This much was evident in the first drive a few weeks back. But tonight the thing really came to life. This car now moves way faster than a vehicle of this weight has any right to lol. The throttle response is great, and it pulls and pulls, even with the 2.73 gear in back. I suppose 5° more timing will do that lol, but disconnecting the vac advance I think also plays into it. The tech at Blueprint said I'd notice it, and he was sure right.
I have never been more convinced that I need to do a disc brake conversion in the rear as as am now...she moves quick, now she needs to stop quick too.
I will double check my initial timing again because in all my haste, I never checked to make sure that stayed put. Hoping it will, as the distributor is brand new.
But I guess I'm officially calling this swap complete. Thanks to all who helped me along the way!