As stated above.
I have a complete clutch & bell & 5speed OD setup off an LA 3.9, and I'm considering swapping the 3.9 for a 5.2 Magnum I have found. Will the LA 3.9 flywheel work on the 5.2 magnum motor?

The next issue is the 5.2 is an OBD2 ignition system but the 3.9 is OBD1. The car currently has the OBD1 with the manual trans and it runs well (except for the tired motor). The OBD2 wire harness from the 5.2 is available (in a 4x4 auto truck), but the motor does not run (codes show a bad sensor, but replacing the sensor didn't help). I have not looked into the running issue with the 5.2 running myself, going by what I was told. The 5.2 spins over nicely, and is a free motor if I want it. I would be bolting the manual trans onto the magnum motor.
Thoughts?

Sure it would work in a carbureted application but not efi (at least not stock efi as Mopar used them)
The 3.9 will have 6 notches for the crank sensor where the 8 cyl needs 8 notches. .if you fire the crank sensor off the damper (somehow?) that flywheel should work

Thank you!
Forgot about the flywheel pickup all together,
That was why I asked.

Doesn't appear as though the 3.9 bell nor the trans I have will work on the magnum motor either.
Everything I'm seeing says the flywheel and clutch for a magnum manual trans is an 11" with a flywheel OD of 14.5" and the 3.9 flywheel is 13.5" OD with a 10.5" clutch, unless I look into a different ignition system and ditch the factory stuff. Sure would like to keep the EFI though.

You should find out how many teeth are on each flywheel to see they are the same. Years ago I blew the engine on my 93 Dakota, 3.9, ax15 5 speed. Replace it with a 3.9 out of a 1500 was told. I think both flywheels were the same at 143 teeth but the Dakota was drilled for 10 1/2 and the ram was 11. Which was why I had to switch it

I have discovered some more info, it appears I can remove the current V6 timing ring from the 3.9 flywheel, and use an automatic trans flex plate sandwiched between the flywheel and the crankshaft flange to trigger the timing sensor. Then I can use all the 3.9 stuff on the 5.2 motor and keep the factory ignition. The GV2500 trans might be a bit light duty for the V8, but I have an extra 3.9 flywheel, clutch, & trans I can afford to screw up, as a test subject. Both the 5.2 and the 3.9 flywheels are neutral balanced, but if the 5.2 I have doesn't work out, a 5.9 magnum V8 needs a different different balanced, larger diameter flywheel. Then I may be screwed.

At this point, everything here is in a holding pattern. We have to put a new roof on our house, and until I see those numbers, most unnecessary spending has stopped. That process has been painstakingly slow, but the light at the end of the tunnel is getting brighter.

It now looks like this (hopefully) may be a spring project. As things move forward, I'll keep everyone posted.