The 240 rear axle is shorter (disc to disc) than the 140's unit by about 30mm, so the rear track will change.
Redwood Chair (vale) posted the measurements on TB ages ago but I cant find the post.
YM 1975 164s from chassis number 132567 (which were not really seen in OZ) used the 240 type of rear trailing arm arrangement and the shorter 240 rear axle. See the 164 parts book, Drawing 13152 by the infamous E. Zeilgler shows the layout. Preview below.
So, I'm guessing it will fit your 74 144's underbody mounting points. (Guessing, since I haven't cross-referenced the 164 parts to 240 parts, and I'm not sure, for example, if the panhard rod in the 164 is a 240 type or a 74 140/164 type, or a unique-to-164-YM75 type).
As you know, bush [17] is problematical in 240 rear suspensions and BNE Dynamics have a spherical bearing kit available to replace them.
But there may be another solution: If the twisting motion of the 140's lower control arms is an issue, could you replace the rubber compliance bush and bolt with a spherical bearing in each lower shock mount? Come to think of it, you may need to do the same for the upper shock mount too.
PS: Insofar as melted 740 fuse boxes go, I had to do a repair on the 780's fusebox where the fan motor had cooked the contacts and associated terminals. I fixed it with a fuse holder from Jaycar, some heatshrink tubing, judicious use of the Dremel, and a hell of a lot of Araldite.
