1968 GTS 340 with Carter AVS 4966S

Hi all together,
hope you are well, sry that it took so long to response but here is an update:

I followed almost all your suggestions and first took the radiator out and used acetic acid and let it react for a whole day, flushed it with loads of water and put it back in. Bought a new radiator cap and new hoses, filled the system with water and adjusted the timing and the carb. I managed to get a smooth idling with approx. 800rpm but I was ot able to get it any lower. For me this is fine for now, final adjustments will be done when use a exhasut gas analyzer after the rebuild.

Cooling system flush
In Austria and Europe we only get the cooling fluid from Prestone but not the cooling flush. I found something in an article of a quite famous European classic car magazine (Oldtimer Praxis) from 2008 or something. They tested and recommended a product from a german radiator manufacturer (AKS DASIS) based on amidosulfonic acid. This is proper for aluminium, copper and all kinds of metall. ==> let me know if anoybody is intereated and I will support

I poured it in the cooling system at let it react for five days, in between i started the motor once a day and let it warm up. After I drained and flushed the system for about half an hour straight with fresh water I refilled it with distilled water -> result is great! I mean the heater is now completely fucked but even with a heaviliy leaking heater core may temperature issue improved and even after a while idling temperature did not rise in a critical area.
Next step -> recore of heater incl. heat exchanger for heating (cause this on is now also leaking)

Quarter window regulator repair
Whilst I was waiting on parts, chemicals and so on I reworked the quarter window regulators incl. a fresh set of rollers => regulators work great again!

Repair Manual
FYI: rockauto sells licenced reprints for a pretty decent price, got me one => great!

Next steps
removing all mounted parts from the engine and remove engine, put it on a engine stand and renew all gaskets, waterpump, fuel pump, oil pump etc.

Questions: The typical engine lift plate looks a bit fragile from my point of view. I want to remove engine and transmission combined does this really work? Do you recommend a balancer?
What bolts should I use for the engine stand? I would like to order them upfront because bolts in inch are not that easiliy to get in Austria.

Thanks a lot!
Best
Christian