340 marine engines.

[Professor Fate]

Do NOT use a reverse rotation crank in a car application- it will run fine, but the "knurling" on the rear main seal journal is in the opposite direction. Intended to help move oil away from the seal and prevent leaks, a RR crank run in standard rotation will actually force oil OUT past the seal.
If I remember correctly, a reverse rotation engine will have "RR" stamped on the front of the block below the left cylinder head along with the rest of the engine info.

 

[67Dart273]

I think Direct drive prop boats use reverse rotation. I don't think IO's do. (inboard/outboard)
@71GSSDemon wil know I bet.

Inboards came both ways. I've forgotten the explanation. It may have been the preferred side of the boat the driver wanted to pilot from

 

[67Dart273]

It is easy to identify a reverse rotation Mopar engine IF it is together and "as original." They have a tall adapter that the distributor sits in, with a thrust bearing inside, because the thrust in reverse, tries to push up on the drive gear. ---To the left in the photo

 

[67Dart273]

Read this thread on marine engines

Marine 360?

Hi, I have got a 360 bare block that I'm starting to think is or was a reverse rotation marine one, the bore size is +.025", that is weird enough, the stamped # on the front of the block is 5 or 6 numbers stamped vertically instead of just under the deck. What has pointed me to marine is the...

www.forabodiesonly.com

 

[Professor Fate]

It is easy to identify a reverse rotation Mopar engine IF it is together and "as original." They have a tall adapter that the distributor sits in, with a thrust bearing inside, because the thrust in reverse, tries to push up on the drive gear. ---To the left in the photo

View attachment 1716040407

View attachment 1716040409

And if I'm not mistaken (it's been a looong time), the adapter allows use of a 383 distributor (turns opposite of a small block) so the advance mechanism works...