Dan,

I did this exact same rebuild on the same engine (assume Universal M25) last year.  I bought my rebuild kit from Kumar (​http://www.kumarbrosusa.com/kubota/overhaul-kit-d850-std-with-liners.html) and everything fit perfect.  At ~$650, its a pretty economical way of extending the life of your engine.  For the sake of transparency, I am a licenesed engineering marine officer that went to school and worked on ships but I will say it is a pretty simple rebuild.  It took me two weekends which also included painting the engine.  For painting, I highly reommend the Por system kit (http://www.por15.com/ENGINE-PAINTING-KIT_p_49.html), the results were incredible.

I would suggest taking pictures as you go as some of the maintenance manual diagram are not as clear as they could be.  See attached pictures for before and after.
 

I am in the midst of putting a new M25xpb in my boat so I have limited time to write an article about the rebuild but hopefully this summer I can put something together.  Note that my m25 rebuild went great and the engine was running great but an opportunity for a free brand new engine fell in my lap and could not pass it up.  Sold the M25 rebuilt engine to a good home.

As for the pulley kit, I got it from Electromaxx.  The serpentine belt runs a 140 Amp electromaxx alternator.  It really has changed the way my family cruises.  I am putting together an article on the pulley, alternator, and voltage regulator installation now on the new engine.  The voltage regulator will be electromaxx's new one which has the added advantage of quickly and remotely (no magnetic reed switches) lowering the charge rate when you need a bit more power out of the engine while you are charging.  Happy to answer any questions out there.

Ben, I found this from another website thread and thought you may/might be interested ?

How do I align my engine?
Universal inboard marine engines should be installed so that the engine
mounts are securely attached using the correct fasteners, aligned with the
propeller shaft to a tolerance of .05 mm (.002 in) per inch of shaft flange
diameter, measured at the engine and propeller shaft flange face, with the
propeller shaft aligned and centered with the propeller shaft strut cutlass
bearing and stern tube. During adjustment any flexible (ie rubber) engine
mounts should be extended using pry bars or wedges to bring the engine into
the same position it will be when the boat is under power at normal cruising
speed. To determine engine mount deflection position under power, measure
the position of the engine close to each mount with the engine stopped, and
then measure it again under power (you can do this tied to the dock) using a
dial gauge or fixed pointer. Excessive deflection of the engine under power
may mean the engine mounts are loose or the flexible engine mount material
is worn out.
When aligning the engine, adjust the alignment with the 2 rear engine mounts
and 1 forward mount (for V drive engines adjust 1 rear engine mount and 2
forward mounts), leaving the 4th mount loose until the alignment is correct.
Take up the clearance on the 4th mount with the lower adjusting nut or
shims. Then tighten all 4 mount top nuts. This will prevent the engine
block/pan from being twisted (and possibly cracked) during final tightening
of the mount nuts. If the alignment changes when the top nuts are tightened,
the 4th mount clearance was adjusted either too much or not enough. Engine
mount deflection and engine alignment should be checked once per year, as
well as whenever the boat has been lifted from the water, and mounts
replaced or tightened and alignment adjusted as required. Always use
“shakeproof” lock washers on engine mount nuts