I have a 1997 non vvti LS400 that I blew up a couple of years back which I no longer have the engine for.I am having a ton of issues trying to find a 95-97 engine to just drop back into it without issues. I was wondering if anyone could guide me in the right direction for a swap. Looking at JDM non vvti engines, earlier year engines, or even doing a 3UZ swap if it is manageable in the non vvti vehicles.

 

If you're looking the 3UZ route, it's fairly well documented and has been done by a few members:
https://www.clublexus.com/forums/ls-...nto-ls400.html

Not sure what to advise on JDM imported engines.

 

I'm fairly certain 95 - 97 (pre VVTi) heads would not bolt up to a 3UZ block.
Also skeptical an A340E transmission is plug and play with 3UZ...

 

Prop shaft was also (slightly) changed in 98.

3UZ most easily goes into a 98+; earlier cars have more and more differences. Not insurmountable, but each change requires an adjustment\modification.

 

Manageable is a tricky word. It certainly would be lots less trouble with a 95-97 engine. Just drop in a good engine and you're good to go. Not really sure if earlier engines would be a problem, my guess would be minor issues, but maybe some others can help with that.
With a VVTI swap you would have to consider transmissions too as the ECM controls the transmissions as well as the engine. The A340E transmission that bradland highlighted would not be able to be run through a VVTI ECM. I believe the way to do that is to use both your 97 and the VVTI ECM's, having someone knowledgeable redo the wiring harness to accomodate both ECMs. But if you're going to that much trouble and re-wiring a bunch of stuff, you might as well do the upgrade to the A650 five speed trans, either with the 98-00 1UZ engine or the 01-03 3UZ.
Another possibility, if you're considering both trans and engine swaps would be to the 2004-2006 LS430 3UZ/A761E trans combo. You'd still need someone to do the wiring of the two ecms, but it would net you a 6 speed transmission as well as the torque bump of the 3UZ vvti engine. And with that generation ecm you can have it re-flashed for even more performance.
Just a thought...
And please do correct me if I'm wrong.