So was the TD the drive shaft out of, a 617 engine? if so, it should work w/o any cutting. Did you happen to get the 617 flywheel?
The 240 FW will work, but what I have read, the 617 FW will smooth things out, as it is 10# heavier.
That auto trans is heavy, don`y try to strong arm it out. Now the manual trans isn`t bad at all. I`ve pulled 2 out of PNP cars.
You know about getting the manual FW matched balanced to the balance of the auto FW?
when I did the swap on the 300D, my front end came up quite a bit. made the front end wander. I replaced the front springs with 240D front springs.
Now I have a TD front sway bar to install, to correct the softness of the front end when driving on these windy mountain roads. at least you already have the TD bar installed

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Charlie
Charlie