Other than the pistons and rockers, a V-10 is NOTHING like a V-8 Magnum!
They use a deep skirt block, similar design to a big block.
The oil pump is in the timing cover, driven by the crank.
Timing components are one off for the V-10.
They use a specific flywheel, stick or auto.
Connecting rods are different.
Crank stroke is different.
Bellhousing pattern is the same as Cummins.
I have a '97 V-10 sitting here, as well as a 46RH automatic, and it would be an act of extreme creativity to shoehorn both into an A body, BUT, if you used the '89-'91 diesel 727 with the car style extension pieces, it would make the fitment MUCH easier to attempt, as you likely wouldn't have to modify the transmission//torsion bar cross member.
As far as it being longer, I believe it's the same length from bell to fan mount as a slant 6, though I should go measure.
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Mark.