Were crankshafts in 340 engines typically drilled for pilot bushings even if they came with an automatic?

As far as I know, yes. But there are exceptions.

All I have seen have a hole in the crank for a bushing, the issue is that it is not a finished hole sometimes, if you get a stock bushing many times it will not fit. I always just chuck a bushing in a lathe and turn the outside to fit the hole I have. I have seen shade tree guys slip a bushing on a dowel and hold against a grinding wheel to reduce the outside dimension as well. Somebody used to make a thinner one, but the company name I don't remember. I just use my lathe to make them fit.

Not always, maybe half or less is what I have seen on the west coast cars

About three quarters of the auto cranks I've come across aren't drilled. The hole is roughed in but it's not finished.

I've finished several of them. If you have a lathe it's fairly easy.

There is a bushing for the unfinished cranks.

https://www.ebay.com/itm/New-Undersize-P...40/263917067931

The word I heard was that the forged cranks up to '71 were usually finished whether auto or manual and cast cranks after that were only done for manuals. But I'm sure there are exceptions.

Doesn't matter if you use the modern alternative from the Magnum that is backward compatible to the LA. If using the new bearing, I'd make sure to remove the bronze one if it is present.
http://www.brewersperformance.com/proddetail.php?prod=PB5300

ROCKAUTO has that bearing for a lot less. It is ll I have used for years. Just make sure pilot hole is deep enough for trans input shaft. Don't cut off the input shaft drill the hole deeper.

I had a customer that used one of those. It kept breaking the bearing retainer. After verifying the bell was indicated in, we found the bore in the crank was off.

I just made a bushing that went in the converter register and that fixed that. It's the only time I've seen that happen.

Dakota truck roller bearing fits in the crank register too.