locating the transmission mounts is the LAST thing you do in 245 install.
install diff loosely, install DS and guibo
support back of trans with a jack or something
make sure right side engine mounts are LOOSE to help moving trans.
now...COMPLETELY IGNORE ANY ALIGNMENT WITH THE DIFF!!!!!! do not use any "DS alignment jig" that goes length of DS. worthless.
the ONLY thing that matters is that the output flange of the trans and the input flange of the DS are square to each other.
move the back of the trans and the CSB up and down, back and forth to get those flanges square. this can be done by eye, but the 2002sonly tool makes it easy.
once they are square, you will now know where the back of the trans should be and where the CSB will need to be.
the front and back half of the DS DO NOT need to be aligned. there can, and probably will, be a slight kink at the universal joint. that is ok. that is what it is there for.
BTW, in EVERY 245 install i have done(including with an S14), the transmission ended up jammed all the way to driver side of tunnel and all the way up against the top of the tunnel. the CSB's all ended up needing to be moved all the way to passenger side and lowered below the bracket by a few washers.