OK to use synthetic oil in 1941 Chrysler?

smooth and the Fluid Drive is

in the Fluid Drive?

The only wild guess I could make is that it should be fine as a lubricant if you choose the proper weight oil but it might cause older gaskets to weep and leak. Perhaps a 50/50 mix of synthetic and regular oil would be best? I'll leave it to the experts.

Why would you want to do that?

The advantages of synthetic oils are based on how much and how 'hard' they are used. You aren't planning on using this engine much or hard. The only advantage might be the advantage of the synthetic cold start wear, and I'm not so sure about that.

One article sez that the oil leaks associated with changing from conventional to synthetic in old engines is related to the detergents clearing the conventional oil varnish 'clogging' a leak site rather than hurting the actual seal.

I wouldn't. It's not wise to switch an older engine to sythetic. IMO there would be no advantage anyway.

I would put DuraLube in the engine though.

smooth and the Fluid Drive is

in the Fluid Drive?

Just on superstition alone, I'd probably avoid the Group IV PAO synthetics like Mobil 1, Royal Purple, Redline, etc. If you go with the Group III synthetics like Pennzoil Platinum, Valvoline, or Shell Rotella T Synthetic (my preference) then you're still dealing with base oils made from petroleum (although highly refined and modified) instead of PAO oils made from natural gas. I don't know how much oil your flathead burns, but mine always tended to sip a bit more oil than modern engines. The PAOs sometimes cause combustion chamber deposits that other oils don't in engines that burn oil. That is why Mazda still says "no synthetics" in the RX-8 rotary engines, which deliberately burn oil to lubricate the apex seals.